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v3.15.0b2
Doc/library/datetime.rst
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Stan Ulbrych
GH-70647: Remove support for `%d` (and deprecate for `%e`) without year in `strptime()` (GH-144570)
15 апр 2026, 03:15
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15 апр 2026, 03:15
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:mod:`!datetime` --- Basic date and time types ============================================== .. module:: datetime :synopsis: Basic date and time types. **Source code:** :source:`Lib/datetime.py` -------------- The :mod:`!datetime` module supplies classes for manipulating dates and times. While date and time arithmetic is supported, the focus of the implementation is on efficient attribute extraction for output formatting and manipulation. .. tip:: Skip to :ref:`the format codes <format-codes>`. .. seealso:: Module :mod:`calendar` General calendar related functions. Module :mod:`time` Time access and conversions. Module :mod:`zoneinfo` Concrete time zones representing the IANA time zone database. Package `dateutil <https://dateutil.readthedocs.io/en/stable/>`_ Third-party library with expanded time zone and parsing support. Package :pypi:`DateType` Third-party library that introduces distinct static types to for example, allow :term:`static type checkers <static type checker>` to differentiate between naive and aware datetimes. .. _datetime-naive-aware: Aware and naive objects ----------------------- Date and time objects may be categorized as "aware" or "naive" depending on whether or not they include time zone information. With sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, an **aware** object can locate itself relative to other aware objects. An aware object represents a specific moment in time that is not open to interpretation. [#]_ A **naive** object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other time zone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality. For applications requiring aware objects, :class:`.datetime` and :class:`.time` objects have an optional time zone information attribute, :attr:`!tzinfo`, that can be set to an instance of a subclass of the abstract :class:`!tzinfo` class. These :class:`tzinfo` objects capture information about the offset from UTC time, the time zone name, and whether daylight saving time is in effect. Only one concrete :class:`tzinfo` class, the :class:`timezone` class, is supplied by the :mod:`!datetime` module. The :class:`!timezone` class can represent simple time zones with fixed offsets from UTC, such as UTC itself or North American EST and EDT time zones. Supporting time zones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC. Constants --------- The :mod:`!datetime` module exports the following constants: .. data:: MINYEAR The smallest year number allowed in a :class:`date` or :class:`.datetime` object. :const:`MINYEAR` is 1. .. data:: MAXYEAR The largest year number allowed in a :class:`date` or :class:`.datetime` object. :const:`MAXYEAR` is 9999. .. data:: UTC Alias for the UTC time zone singleton :attr:`datetime.timezone.utc`. .. versionadded:: 3.11 Available types --------------- .. class:: date :noindex: An idealized naive date, assuming the current Gregorian calendar always was, and always will be, in effect. Attributes: :attr:`year`, :attr:`month`, and :attr:`day`. .. class:: time :noindex: An idealized time, independent of any particular day, assuming that every day has exactly 24\*60\*60 seconds. (There is no notion of "leap seconds" here.) Attributes: :attr:`hour`, :attr:`minute`, :attr:`second`, :attr:`microsecond`, and :attr:`.tzinfo`. .. class:: datetime :noindex: A combination of a date and a time. Attributes: :attr:`year`, :attr:`month`, :attr:`day`, :attr:`hour`, :attr:`minute`, :attr:`second`, :attr:`microsecond`, and :attr:`.tzinfo`. .. class:: timedelta :noindex: A duration expressing the difference between two :class:`.datetime` or :class:`date` instances to microsecond resolution. .. class:: tzinfo :noindex: An abstract base class for time zone information objects. These are used by the :class:`.datetime` and :class:`.time` classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time). .. class:: timezone :noindex: A class that implements the :class:`tzinfo` abstract base class as a fixed offset from the UTC. .. versionadded:: 3.2 Objects of these types are immutable. Subclass relationships: .. figure:: datetime-inheritance.svg :class: invert-in-dark-mode :align: center :alt: timedelta, tzinfo, time, and date inherit from object; timezone inherits from tzinfo; and datetime inherits from date. Common properties ^^^^^^^^^^^^^^^^^ The :class:`date`, :class:`.datetime`, :class:`.time`, and :class:`timezone` types share these common features: - Objects of these types are immutable. - Objects of these types are :term:`hashable`, meaning that they can be used as dictionary keys. - Objects of these types support efficient pickling via the :mod:`pickle` module. Determining if an object is aware or naive ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Objects of the :class:`date` type are always naive. An object of type :class:`.time` or :class:`.datetime` may be aware or naive. A :class:`.datetime` object ``d`` is aware if both of the following hold: 1. ``d.tzinfo`` is not ``None`` 2. ``d.tzinfo.utcoffset(d)`` does not return ``None`` Otherwise, ``d`` is naive. A :class:`.time` object ``t`` is aware if both of the following hold: 1. ``t.tzinfo`` is not ``None`` 2. ``t.tzinfo.utcoffset(None)`` does not return ``None``. Otherwise, ``t`` is naive. The distinction between aware and naive doesn't apply to :class:`timedelta` objects. .. _datetime-timedelta: :class:`!timedelta` objects --------------------------- A :class:`timedelta` object represents a duration, the difference between two :class:`.datetime` or :class:`date` instances. .. class:: timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0) All arguments are optional and default to 0. Arguments may be integers or floats, and may be positive or negative. Only *days*, *seconds* and *microseconds* are stored internally. Arguments are converted to those units: * A millisecond is converted to 1000 microseconds. * A minute is converted to 60 seconds. * An hour is converted to 3600 seconds. * A week is converted to 7 days. and days, seconds and microseconds are then normalized so that the representation is unique, with * ``0 <= microseconds < 1000000`` * ``0 <= seconds < 3600*24`` (the number of seconds in one day) * ``-999999999 <= days <= 999999999`` The following example illustrates how any arguments besides *days*, *seconds* and *microseconds* are "merged" and normalized into those three resulting attributes:: >>> import datetime as dt >>> delta = dt.timedelta( ... days=50, ... seconds=27, ... microseconds=10, ... milliseconds=29000, ... minutes=5, ... hours=8, ... weeks=2 ... ) >>> # Only days, seconds, and microseconds remain >>> delta datetime.timedelta(days=64, seconds=29156, microseconds=10) .. tip:: ``import datetime as dt`` instead of ``import datetime`` or ``from datetime import datetime`` to avoid confusion between the module and the class. See `How I Import Python’s datetime Module <https://adamj.eu/tech/2019/09/12/how-i-import-pythons-datetime-module/>`__. If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round-half-to-even tiebreaker. If no argument is a float, the conversion and normalization processes are exact (no information is lost). If the normalized value of days lies outside the indicated range, :exc:`OverflowError` is raised. Note that normalization of negative values may be surprising at first. For example:: >>> import datetime as dt >>> d = dt.timedelta(microseconds=-1) >>> (d.days, d.seconds, d.microseconds) (-1, 86399, 999999) Since the string representation of :class:`!timedelta` objects can be confusing, use the following recipe to produce a more readable format: .. code-block:: pycon >>> def pretty_timedelta(td): ... if td.days >= 0: ... return str(td) ... return f'-({-td!s})' ... >>> d = timedelta(hours=-1) >>> str(d) # not human-friendly '-1 day, 23:00:00' >>> pretty_timedelta(d) '-(1:00:00)' Class attributes: .. attribute:: timedelta.min The most negative :class:`timedelta` object, ``timedelta(-999999999)``. .. attribute:: timedelta.max The most positive :class:`timedelta` object, ``timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999)``. .. attribute:: timedelta.resolution The smallest possible difference between non-equal :class:`timedelta` objects, ``timedelta(microseconds=1)``. Note that, because of normalization, ``timedelta.max`` is greater than ``-timedelta.min``. ``-timedelta.max`` is not representable as a :class:`timedelta` object. Instance attributes (read-only): .. attribute:: timedelta.days Between -999,999,999 and 999,999,999 inclusive. .. attribute:: timedelta.seconds Between 0 and 86,399 inclusive. .. caution:: It is a somewhat common bug for code to unintentionally use this attribute when it is actually intended to get a :meth:`~timedelta.total_seconds` value instead: .. doctest:: >>> import datetime as dt >>> duration = dt.timedelta(seconds=11235813) >>> duration.days, duration.seconds (130, 3813) >>> duration.total_seconds() 11235813.0 .. attribute:: timedelta.microseconds Between 0 and 999,999 inclusive. Supported operations: +--------------------------------+-----------------------------------------------+ | Operation | Result | +================================+===============================================+ | ``t1 = t2 + t3`` | Sum of ``t2`` and ``t3``. | | | Afterwards ``t1 - t2 == t3`` and | | | ``t1 - t3 == t2`` are true. (1) | +--------------------------------+-----------------------------------------------+ | ``t1 = t2 - t3`` | Difference of ``t2`` and ``t3``. Afterwards | | | ``t1 == t2 - t3`` and ``t2 == t1 + t3`` are | | | true. (1)(6) | +--------------------------------+-----------------------------------------------+ | ``t1 = t2 * i or t1 = i * t2`` | Delta multiplied by an integer. | | | Afterwards ``t1 // i == t2`` is true, | | | provided ``i != 0``. | +--------------------------------+-----------------------------------------------+ | | In general, ``t1 * i == t1 * (i-1) + t1`` | | | is true. (1) | +--------------------------------+-----------------------------------------------+ | ``t1 = t2 * f or t1 = f * t2`` | Delta multiplied by a float. The result is | | | rounded to the nearest multiple of | | | timedelta.resolution using round-half-to-even.| +--------------------------------+-----------------------------------------------+ | ``f = t2 / t3`` | Division (3) of overall duration ``t2`` by | | | interval unit ``t3``. Returns a :class:`float`| | | object. | +--------------------------------+-----------------------------------------------+ | ``t1 = t2 / f or t1 = t2 / i`` | Delta divided by a float or an int. The result| | | is rounded to the nearest multiple of | | | timedelta.resolution using round-half-to-even.| +--------------------------------+-----------------------------------------------+ | ``t1 = t2 // i`` or | The floor is computed and the remainder (if | | ``t1 = t2 // t3`` | any) is thrown away. In the second case, an | | | integer is returned. (3) | +--------------------------------+-----------------------------------------------+ | ``t1 = t2 % t3`` | The remainder is computed as a | | | :class:`timedelta` object. (3) | +--------------------------------+-----------------------------------------------+ | ``q, r = divmod(t1, t2)`` | Computes the quotient and the remainder: | | | ``q = t1 // t2`` (3) and ``r = t1 % t2``. | | | ``q`` is an integer and ``r`` is a | | | :class:`timedelta` object. | +--------------------------------+-----------------------------------------------+ | ``+t1`` | Returns a :class:`timedelta` object with the | | | same value. (2) | +--------------------------------+-----------------------------------------------+ | ``-t1`` | Equivalent to ``timedelta(-t1.days, | | | -t1.seconds, -t1.microseconds)``, | | | and to ``t1 * -1``. (1)(4) | +--------------------------------+-----------------------------------------------+ | ``abs(t)`` | Equivalent to ``+t`` when ``t.days >= 0``, | | | and to ``-t`` when ``t.days < 0``. (2) | +--------------------------------+-----------------------------------------------+ | ``str(t)`` | Returns a string in the form | | | ``[D day[s], ][H]H:MM:SS[.UUUUUU]``, where D | | | is negative for negative ``t``. (5) | +--------------------------------+-----------------------------------------------+ | ``repr(t)`` | Returns a string representation of the | | | :class:`timedelta` object as a constructor | | | call with canonical attribute values. | +--------------------------------+-----------------------------------------------+ Notes: (1) This is exact but may overflow. (2) This is exact and cannot overflow. (3) Division by zero raises :exc:`ZeroDivisionError`. (4) ``-timedelta.max`` is not representable as a :class:`timedelta` object. (5) String representations of :class:`timedelta` objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example:: >>> timedelta(hours=-5) datetime.timedelta(days=-1, seconds=68400) >>> print(_) -1 day, 19:00:00 (6) The expression ``t2 - t3`` will always be equal to the expression ``t2 + (-t3)`` except when t3 is equal to ``timedelta.max``; in that case the former will produce a result while the latter will overflow. In addition to the operations listed above, :class:`timedelta` objects support certain additions and subtractions with :class:`date` and :class:`.datetime` objects (see below). .. versionchanged:: 3.2 Floor division and true division of a :class:`timedelta` object by another :class:`!timedelta` object are now supported, as are remainder operations and the :func:`divmod` function. True division and multiplication of a :class:`!timedelta` object by a :class:`float` object are now supported. :class:`timedelta` objects support equality and order comparisons. In Boolean contexts, a :class:`timedelta` object is considered to be true if and only if it isn't equal to ``timedelta(0)``. Instance methods: .. method:: timedelta.total_seconds() Return the total number of seconds contained in the duration. Equivalent to ``td / timedelta(seconds=1)``. For interval units other than seconds, use the division form directly (for example, ``td / timedelta(microseconds=1)``). Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy. .. versionadded:: 3.2 Examples of usage: :class:`!timedelta` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ An additional example of normalization:: >>> # Components of another_year add up to exactly 365 days >>> import datetime as dt >>> year = dt.timedelta(days=365) >>> another_year = dt.timedelta(weeks=40, days=84, hours=23, ... minutes=50, seconds=600) >>> year == another_year True >>> year.total_seconds() 31536000.0 Examples of :class:`timedelta` arithmetic:: >>> import datetime as dt >>> year = dt.timedelta(days=365) >>> ten_years = 10 * year >>> ten_years datetime.timedelta(days=3650) >>> ten_years.days // 365 10 >>> nine_years = ten_years - year >>> nine_years datetime.timedelta(days=3285) >>> three_years = nine_years // 3 >>> three_years, three_years.days // 365 (datetime.timedelta(days=1095), 3) .. _datetime-date: :class:`!date` objects ---------------------- A :class:`date` object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions. January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. [#]_ .. class:: date(year, month, day) All arguments are required. Arguments must be integers, in the following ranges: * ``MINYEAR <= year <= MAXYEAR`` * ``1 <= month <= 12`` * ``1 <= day <= number of days in the given month and year`` If an argument outside those ranges is given, :exc:`ValueError` is raised. Other constructors, all class methods: .. classmethod:: date.today() Return the current local date. This is equivalent to ``date.fromtimestamp(time.time())``. .. classmethod:: date.fromtimestamp(timestamp) Return the local date corresponding to the POSIX *timestamp*, such as is returned by :func:`time.time`. This may raise :exc:`OverflowError`, if the timestamp is out of the range of values supported by the platform C :c:func:`localtime` function, and :exc:`OSError` on :c:func:`localtime` failure. It's common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by :meth:`fromtimestamp`. .. versionchanged:: 3.3 Raise :exc:`OverflowError` instead of :exc:`ValueError` if the timestamp is out of the range of values supported by the platform C :c:func:`localtime` function. Raise :exc:`OSError` instead of :exc:`ValueError` on :c:func:`localtime` failure. .. versionchanged:: 3.15 Accepts any real number as *timestamp*, not only integer or float. .. classmethod:: date.fromordinal(ordinal) Return the date corresponding to the proleptic Gregorian *ordinal*, where January 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1 <= ordinal <= date.max.toordinal()``. For any date ``d``, ``date.fromordinal(d.toordinal()) == d``. .. classmethod:: date.fromisoformat(date_string) Return a :class:`date` corresponding to a *date_string* given in any valid ISO 8601 format, with the following exceptions: 1. Reduced precision dates are not currently supported (``YYYY-MM``, ``YYYY``). 2. Extended date representations are not currently supported (``±YYYYYY-MM-DD``). 3. Ordinal dates are not currently supported (``YYYY-OOO``). Examples:: >>> import datetime as dt >>> dt.date.fromisoformat('2019-12-04') datetime.date(2019, 12, 4) >>> dt.date.fromisoformat('20191204') datetime.date(2019, 12, 4) >>> dt.date.fromisoformat('2021-W01-1') datetime.date(2021, 1, 4) .. versionadded:: 3.7 .. versionchanged:: 3.11 Previously, this method only supported the format ``YYYY-MM-DD``. .. classmethod:: date.fromisocalendar(year, week, day) Return a :class:`date` corresponding to the ISO calendar date specified by *year*, *week* and *day*. This is the inverse of the function :meth:`date.isocalendar`. .. versionadded:: 3.8 .. classmethod:: date.strptime(date_string, format) Return a :class:`.date` corresponding to *date_string*, parsed according to *format*. This is equivalent to:: date(*(time.strptime(date_string, format)[0:3])) :exc:`ValueError` is raised if the date_string and format can't be parsed by :func:`time.strptime` or if it returns a value which isn't a time tuple. See also :ref:`strftime-strptime-behavior` and :meth:`date.fromisoformat`. .. note:: If *format* specifies a day of month (``%d``) without a year, :exc:`ValueError` is raised. This is to avoid a quadrennial leap year bug in code seeking to parse only a month and day as the default year used in absence of one in the format is not a leap year. The workaround is to always include a year in your *format*. If parsing *date_string* values that do not have a year, explicitly add a year that is a leap year before parsing: .. doctest:: >>> import datetime as dt >>> date_string = "02/29" >>> when = dt.date.strptime(f"{date_string};1984", "%m/%d;%Y") # Avoids leap year bug. >>> when.strftime("%B %d") # doctest: +SKIP 'February 29' .. versionadded:: 3.14 Class attributes: .. attribute:: date.min The earliest representable date, ``date(MINYEAR, 1, 1)``. .. attribute:: date.max The latest representable date, ``date(MAXYEAR, 12, 31)``. .. attribute:: date.resolution The smallest possible difference between non-equal date objects, ``timedelta(days=1)``. Instance attributes (read-only): .. attribute:: date.year Between :const:`MINYEAR` and :const:`MAXYEAR` inclusive. .. attribute:: date.month Between 1 and 12 inclusive. .. attribute:: date.day Between 1 and the number of days in the given month of the given year. Supported operations: +-------------------------------+----------------------------------------------+ | Operation | Result | +===============================+==============================================+ | ``date2 = date1 + timedelta`` | ``date2`` will be ``timedelta.days`` days | | | after ``date1``. (1) | +-------------------------------+----------------------------------------------+ | ``date2 = date1 - timedelta`` | Computes ``date2`` such that ``date2 + | | | timedelta == date1``. (2) | +-------------------------------+----------------------------------------------+ | ``timedelta = date1 - date2`` | \(3) | +-------------------------------+----------------------------------------------+ | | ``date1 == date2`` | Equality comparison. (4) | | | ``date1 != date2`` | | +-------------------------------+----------------------------------------------+ | | ``date1 < date2`` | Order comparison. (5) | | | ``date1 > date2`` | | | | ``date1 <= date2`` | | | | ``date1 >= date2`` | | +-------------------------------+----------------------------------------------+ Notes: (1) *date2* is moved forward in time if ``timedelta.days > 0``, or backward if ``timedelta.days < 0``. Afterward ``date2 - date1 == timedelta.days``. ``timedelta.seconds`` and ``timedelta.microseconds`` are ignored. :exc:`OverflowError` is raised if ``date2.year`` would be smaller than :const:`MINYEAR` or larger than :const:`MAXYEAR`. (2) ``timedelta.seconds`` and ``timedelta.microseconds`` are ignored. (3) This is exact, and cannot overflow. ``timedelta.seconds`` and ``timedelta.microseconds`` are 0, and ``date2 + timedelta == date1`` after. (4) :class:`date` objects are equal if they represent the same date. :class:`!date` objects that are not also :class:`.datetime` instances are never equal to :class:`!datetime` objects, even if they represent the same date. (5) *date1* is considered less than *date2* when *date1* precedes *date2* in time. In other words, ``date1 < date2`` if and only if ``date1.toordinal() < date2.toordinal()``. Order comparison between a :class:`date` object that is not also a :class:`.datetime` instance and a :class:`!datetime` object raises :exc:`TypeError`. .. versionchanged:: 3.13 Comparison between :class:`.datetime` object and an instance of the :class:`date` subclass that is not a :class:`!datetime` subclass no longer converts the latter to :class:`!date`, ignoring the time part and the time zone. The default behavior can be changed by overriding the special comparison methods in subclasses. In Boolean contexts, all :class:`date` objects are considered to be true. Instance methods: .. method:: date.replace(year=self.year, month=self.month, day=self.day) Return a new :class:`date` object with the same values, but with specified parameters updated. Example:: >>> import datetime as dt >>> d = dt.date(2002, 12, 31) >>> d.replace(day=26) datetime.date(2002, 12, 26) The generic function :func:`copy.replace` also supports :class:`date` objects. .. method:: date.timetuple() Return a :class:`time.struct_time` such as returned by :func:`time.localtime`. The hours, minutes and seconds are 0, and the DST flag is -1. ``d.timetuple()`` is equivalent to:: time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1)) where ``yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1`` is the day number within the current year starting with 1 for January 1st. .. method:: date.toordinal() Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any :class:`date` object ``d``, ``date.fromordinal(d.toordinal()) == d``. .. method:: date.weekday() Return the day of the week as an integer, where Monday is 0 and Sunday is 6. For example, ``date(2002, 12, 4).weekday() == 2``, a Wednesday. See also :meth:`isoweekday`. .. method:: date.isoweekday() Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example, ``date(2002, 12, 4).isoweekday() == 3``, a Wednesday. See also :meth:`weekday`, :meth:`isocalendar`. .. method:: date.isocalendar() Return a :term:`named tuple` object with three components: ``year``, ``week`` and ``weekday``. The ISO calendar is a widely used variant of the Gregorian calendar. [#]_ The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year. For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004:: >>> import datetime as dt >>> dt.date(2003, 12, 29).isocalendar() datetime.IsoCalendarDate(year=2004, week=1, weekday=1) >>> dt.date(2004, 1, 4).isocalendar() datetime.IsoCalendarDate(year=2004, week=1, weekday=7) .. versionchanged:: 3.9 Result changed from a tuple to a :term:`named tuple`. .. method:: date.isoformat() Return a string representing the date in ISO 8601 format, ``YYYY-MM-DD``:: >>> import datetime as dt >>> dt.date(2002, 12, 4).isoformat() '2002-12-04' .. method:: date.__str__() For a date ``d``, ``str(d)`` is equivalent to ``d.isoformat()``. .. method:: date.ctime() Return a string representing the date:: >>> import datetime as dt >>> dt.date(2002, 12, 4).ctime() 'Wed Dec 4 00:00:00 2002' ``d.ctime()`` is equivalent to:: time.ctime(time.mktime(d.timetuple())) on platforms where the native C :c:func:`ctime` function (which :func:`time.ctime` invokes, but which :meth:`date.ctime` does not invoke) conforms to the C standard. .. method:: date.strftime(format) Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. See also :ref:`strftime-strptime-behavior` and :meth:`date.isoformat`. .. method:: date.__format__(format) Same as :meth:`.date.strftime`. This makes it possible to specify a format string for a :class:`.date` object in :ref:`formatted string literals <f-strings>` and when using :meth:`str.format`. See also :ref:`strftime-strptime-behavior` and :meth:`date.isoformat`. Examples of usage: :class:`!date` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Example of counting days to an event:: >>> import time >>> import datetime as dt >>> today = dt.date.today() >>> today datetime.date(2007, 12, 5) >>> today == dt.date.fromtimestamp(time.time()) True >>> my_birthday = dt.date(today.year, 6, 24) >>> if my_birthday < today: ... my_birthday = my_birthday.replace(year=today.year + 1) ... >>> my_birthday datetime.date(2008, 6, 24) >>> time_to_birthday = abs(my_birthday - today) >>> time_to_birthday.days 202 More examples of working with :class:`date`: .. doctest:: >>> import datetime as dt >>> d = dt.date.fromordinal(730920) # 730920th day after 1. 1. 0001 >>> d datetime.date(2002, 3, 11) >>> # Methods related to formatting string output >>> d.isoformat() '2002-03-11' >>> d.strftime("%d/%m/%y") '11/03/02' >>> d.strftime("%A %d. %B %Y") 'Monday 11. March 2002' >>> d.ctime() 'Mon Mar 11 00:00:00 2002' >>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month") 'The day is 11, the month is March.' >>> # Methods for extracting 'components' under different calendars >>> t = d.timetuple() >>> for i in t: # doctest: +SKIP ... print(i) 2002 # year 3 # month 11 # day 0 0 0 0 # weekday (0 = Monday) 70 # 70th day in the year -1 >>> ic = d.isocalendar() >>> for i in ic: # doctest: +SKIP ... print(i) 2002 # ISO year 11 # ISO week number 1 # ISO day number ( 1 = Monday ) >>> # A date object is immutable; all operations produce a new object >>> d.replace(year=2005) datetime.date(2005, 3, 11) .. _datetime-datetime: :class:`!datetime` objects -------------------------- A :class:`.datetime` object is a single object containing all the information from a :class:`date` object and a :class:`.time` object. Like a :class:`date` object, :class:`.datetime` assumes the current Gregorian calendar extended in both directions; like a :class:`.time` object, :class:`!datetime` assumes there are exactly 3600\*24 seconds in every day. Constructor: .. class:: datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0) The *year*, *month* and *day* arguments are required. *tzinfo* may be ``None``, or an instance of a :class:`tzinfo` subclass. The remaining arguments must be integers in the following ranges: * ``MINYEAR <= year <= MAXYEAR``, * ``1 <= month <= 12``, * ``1 <= day <= number of days in the given month and year``, * ``0 <= hour < 24``, * ``0 <= minute < 60``, * ``0 <= second < 60``, * ``0 <= microsecond < 1000000``, * ``fold in [0, 1]``. If an argument outside those ranges is given, :exc:`ValueError` is raised. .. versionchanged:: 3.6 Added the *fold* parameter. Other constructors, all class methods: .. classmethod:: datetime.today() Return the current local date and time, with :attr:`.tzinfo` ``None``. Equivalent to:: datetime.fromtimestamp(time.time()) See also :meth:`now`, :meth:`fromtimestamp`. This method is functionally equivalent to :meth:`now`, but without a ``tz`` parameter. .. classmethod:: datetime.now(tz=None) Return the current local date and time. If optional argument *tz* is ``None`` or not specified, this is like :meth:`today`, but, if possible, supplies more precision than can be gotten from going through a :func:`time.time` timestamp (for example, this may be possible on platforms supplying the C :c:func:`gettimeofday` function). If *tz* is not ``None``, it must be an instance of a :class:`tzinfo` subclass, and the current date and time are converted to *tz*’s time zone. This function is preferred over :meth:`today` and :meth:`utcnow`. .. note:: Subsequent calls to :meth:`!datetime.now` may return the same instant depending on the precision of the underlying clock. .. classmethod:: datetime.utcnow() Return the current UTC date and time, with :attr:`.tzinfo` ``None``. This is like :meth:`now`, but returns the current UTC date and time, as a naive :class:`.datetime` object. An aware current UTC datetime can be obtained by calling ``datetime.now(timezone.utc)``. See also :meth:`now`. .. warning:: Because naive ``datetime`` objects are treated by many ``datetime`` methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing the current time in UTC is by calling ``datetime.now(timezone.utc)``. .. deprecated:: 3.12 Use :meth:`datetime.now` with :const:`UTC` instead. .. classmethod:: datetime.fromtimestamp(timestamp, tz=None) Return the local date and time corresponding to the POSIX timestamp, such as is returned by :func:`time.time`. If optional argument *tz* is ``None`` or not specified, the timestamp is converted to the platform's local date and time, and the returned :class:`.datetime` object is naive. If *tz* is not ``None``, it must be an instance of a :class:`tzinfo` subclass, and the timestamp is converted to *tz*’s time zone. :meth:`fromtimestamp` may raise :exc:`OverflowError`, if the timestamp is out of the range of values supported by the platform C :c:func:`localtime` or :c:func:`gmtime` functions, and :exc:`OSError` on :c:func:`localtime` or :c:func:`gmtime` failure. It's common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by :meth:`fromtimestamp`, and then it's possible to have two timestamps differing by a second that yield identical :class:`.datetime` objects. This method is preferred over :meth:`utcfromtimestamp`. .. versionchanged:: 3.3 Raise :exc:`OverflowError` instead of :exc:`ValueError` if the timestamp is out of the range of values supported by the platform C :c:func:`localtime` or :c:func:`gmtime` functions. Raise :exc:`OSError` instead of :exc:`ValueError` on :c:func:`localtime` or :c:func:`gmtime` failure. .. versionchanged:: 3.6 :meth:`fromtimestamp` may return instances with :attr:`.fold` set to 1. .. versionchanged:: 3.15 Accepts any real number as *timestamp*, not only integer or float. .. classmethod:: datetime.utcfromtimestamp(timestamp) Return the UTC :class:`.datetime` corresponding to the POSIX timestamp, with :attr:`.tzinfo` ``None``. (The resulting object is naive.) This may raise :exc:`OverflowError`, if the timestamp is out of the range of values supported by the platform C :c:func:`gmtime` function, and :exc:`OSError` on :c:func:`gmtime` failure. It's common for this to be restricted to years in 1970 through 2038. To get an aware :class:`.datetime` object, call :meth:`fromtimestamp`:: datetime.fromtimestamp(timestamp, timezone.utc) On the POSIX compliant platforms, it is equivalent to the following expression:: datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp) except the latter formula always supports the full years range: between :const:`MINYEAR` and :const:`MAXYEAR` inclusive. .. warning:: Because naive ``datetime`` objects are treated by many ``datetime`` methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing a specific timestamp in UTC is by calling ``datetime.fromtimestamp(timestamp, tz=timezone.utc)``. .. versionchanged:: 3.3 Raise :exc:`OverflowError` instead of :exc:`ValueError` if the timestamp is out of the range of values supported by the platform C :c:func:`gmtime` function. Raise :exc:`OSError` instead of :exc:`ValueError` on :c:func:`gmtime` failure. .. versionchanged:: 3.15 Accepts any real number as *timestamp*, not only integer or float. .. deprecated:: 3.12 Use :meth:`datetime.fromtimestamp` with :const:`UTC` instead. .. classmethod:: datetime.fromordinal(ordinal) Return the :class:`.datetime` corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1 <= ordinal <= datetime.max.toordinal()``. The hour, minute, second and microsecond of the result are all 0, and :attr:`.tzinfo` is ``None``. .. classmethod:: datetime.combine(date, time, tzinfo=time.tzinfo) Return a new :class:`.datetime` object whose date components are equal to the given :class:`date` object's, and whose time components are equal to the given :class:`.time` object's. If the *tzinfo* argument is provided, its value is used to set the :attr:`.tzinfo` attribute of the result, otherwise the :attr:`~.time.tzinfo` attribute of the *time* argument is used. If the *date* argument is a :class:`!datetime` object, its time components and :attr:`.tzinfo` attributes are ignored. For any :class:`.datetime` object ``d``, ``d == datetime.combine(d.date(), d.time(), d.tzinfo)``. .. versionchanged:: 3.6 Added the *tzinfo* argument. .. classmethod:: datetime.fromisoformat(date_string) Return a :class:`.datetime` corresponding to a *date_string* in any valid ISO 8601 format, with the following exceptions: 1. Time zone offsets may have fractional seconds. 2. The ``T`` separator may be replaced by any single unicode character. 3. Fractional hours and minutes are not supported. 4. Reduced precision dates are not currently supported (``YYYY-MM``, ``YYYY``). 5. Extended date representations are not currently supported (``±YYYYYY-MM-DD``). 6. Ordinal dates are not currently supported (``YYYY-OOO``). Examples:: >>> import datetime as dt >>> dt.datetime.fromisoformat('2011-11-04') datetime.datetime(2011, 11, 4, 0, 0) >>> dt.datetime.fromisoformat('20111104') datetime.datetime(2011, 11, 4, 0, 0) >>> dt.datetime.fromisoformat('2011-11-04T00:05:23') datetime.datetime(2011, 11, 4, 0, 5, 23) >>> dt.datetime.fromisoformat('2011-11-04T00:05:23Z') datetime.datetime(2011, 11, 4, 0, 5, 23, tzinfo=datetime.timezone.utc) >>> dt.datetime.fromisoformat('20111104T000523') datetime.datetime(2011, 11, 4, 0, 5, 23) >>> dt.datetime.fromisoformat('2011-W01-2T00:05:23.283') datetime.datetime(2011, 1, 4, 0, 5, 23, 283000) >>> dt.datetime.fromisoformat('2011-11-04 00:05:23.283') datetime.datetime(2011, 11, 4, 0, 5, 23, 283000) >>> dt.datetime.fromisoformat('2011-11-04 00:05:23.283+00:00') datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc) >>> dt.datetime.fromisoformat('2011-11-04T00:05:23+04:00') # doctest: +NORMALIZE_WHITESPACE datetime.datetime(2011, 11, 4, 0, 5, 23, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400))) .. versionadded:: 3.7 .. versionchanged:: 3.11 Previously, this method only supported formats that could be emitted by :meth:`date.isoformat` or :meth:`datetime.isoformat`. .. classmethod:: datetime.fromisocalendar(year, week, day) Return a :class:`.datetime` corresponding to the ISO calendar date specified by *year*, *week* and *day*. The non-date components of the datetime are populated with their normal default values. This is the inverse of the function :meth:`datetime.isocalendar`. .. versionadded:: 3.8 .. classmethod:: datetime.strptime(date_string, format) Return a :class:`.datetime` corresponding to *date_string*, parsed according to *format*. If *format* does not contain microseconds or time zone information, this is equivalent to:: datetime(*(time.strptime(date_string, format)[0:6])) :exc:`ValueError` is raised if the date_string and format can't be parsed by :func:`time.strptime` or if it returns a value which isn't a time tuple. See also :ref:`strftime-strptime-behavior` and :meth:`datetime.fromisoformat`. .. versionchanged:: 3.15 If *format* specifies a day of month (``%d``) without a year, :exc:`ValueError` is raised. This is to avoid a quadrennial leap year bug in code seeking to parse only a month and day as the default year used in absence of one in the format is not a leap year. The workaround is to always include a year in your *format*. If parsing *date_string* values that do not have a year, explicitly add a year that is a leap year before parsing: .. doctest:: >>> import datetime as dt >>> date_string = "02/29" >>> when = dt.datetime.strptime(f"{date_string};1984", "%m/%d;%Y") # Avoids leap year bug. >>> when.strftime("%B %d") # doctest: +SKIP 'February 29' Class attributes: .. attribute:: datetime.min The earliest representable :class:`.datetime`, ``datetime(MINYEAR, 1, 1, tzinfo=None)``. .. attribute:: datetime.max The latest representable :class:`.datetime`, ``datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None)``. .. attribute:: datetime.resolution The smallest possible difference between non-equal :class:`.datetime` objects, ``timedelta(microseconds=1)``. Instance attributes (read-only): .. attribute:: datetime.year Between :const:`MINYEAR` and :const:`MAXYEAR` inclusive. .. attribute:: datetime.month Between 1 and 12 inclusive. .. attribute:: datetime.day Between 1 and the number of days in the given month of the given year. .. attribute:: datetime.hour In ``range(24)``. .. attribute:: datetime.minute In ``range(60)``. .. attribute:: datetime.second In ``range(60)``. .. attribute:: datetime.microsecond In ``range(1000000)``. .. attribute:: datetime.tzinfo The object passed as the *tzinfo* argument to the :class:`.datetime` constructor, or ``None`` if none was passed. .. attribute:: datetime.fold In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The values 0 and 1 represent, respectively, the earlier and later of the two moments with the same wall time representation. .. versionadded:: 3.6 Supported operations: +---------------------------------------+--------------------------------+ | Operation | Result | +=======================================+================================+ | ``datetime2 = datetime1 + timedelta`` | \(1) | +---------------------------------------+--------------------------------+ | ``datetime2 = datetime1 - timedelta`` | \(2) | +---------------------------------------+--------------------------------+ | ``timedelta = datetime1 - datetime2`` | \(3) | +---------------------------------------+--------------------------------+ | | ``datetime1 == datetime2`` | Equality comparison. (4) | | | ``datetime1 != datetime2`` | | +---------------------------------------+--------------------------------+ | | ``datetime1 < datetime2`` | Order comparison. (5) | | | ``datetime1 > datetime2`` | | | | ``datetime1 <= datetime2`` | | | | ``datetime1 >= datetime2`` | | +---------------------------------------+--------------------------------+ (1) ``datetime2`` is a duration of ``timedelta`` removed from ``datetime1``, moving forward in time if ``timedelta.days > 0``, or backward if ``timedelta.days < 0``. The result has the same :attr:`~.datetime.tzinfo` attribute as the input datetime, and ``datetime2 - datetime1 == timedelta`` after. :exc:`OverflowError` is raised if ``datetime2.year`` would be smaller than :const:`MINYEAR` or larger than :const:`MAXYEAR`. Note that no time zone adjustments are done even if the input is an aware object. (2) Computes the ``datetime2`` such that ``datetime2 + timedelta == datetime1``. As for addition, the result has the same :attr:`~.datetime.tzinfo` attribute as the input datetime, and no time zone adjustments are done even if the input is aware. (3) Subtraction of a :class:`.datetime` from a :class:`!datetime` is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive, :exc:`TypeError` is raised. If both are naive, or both are aware and have the same :attr:`~.datetime.tzinfo` attribute, the :attr:`~.datetime.tzinfo` attributes are ignored, and the result is a :class:`timedelta` object ``t`` such that ``datetime2 + t == datetime1``. No time zone adjustments are done in this case. If both are aware and have different :attr:`~.datetime.tzinfo` attributes, ``a-b`` acts as if ``a`` and ``b`` were first converted to naive UTC datetimes. The result is ``(a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) - b.utcoffset())`` except that the implementation never overflows. (4) :class:`.datetime` objects are equal if they represent the same date and time, taking into account the time zone. Naive and aware :class:`.datetime` objects are never equal. If both comparands are aware, and have the same :attr:`!tzinfo` attribute, the :attr:`!tzinfo` and :attr:`~.datetime.fold` attributes are ignored and the base datetimes are compared. If both comparands are aware and have different :attr:`~.datetime.tzinfo` attributes, the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows. :class:`.datetime` instances in a repeated interval are never equal to :class:`!datetime` instances in other time zone. (5) *datetime1* is considered less than *datetime2* when *datetime1* precedes *datetime2* in time, taking into account the time zone. Order comparison between naive and aware :class:`.datetime` objects raises :exc:`TypeError`. If both comparands are aware, and have the same :attr:`!tzinfo` attribute, the :attr:`!tzinfo` and :attr:`~.datetime.fold` attributes are ignored and the base datetimes are compared. If both comparands are aware and have different :attr:`~.datetime.tzinfo` attributes, the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows. .. versionchanged:: 3.3 Equality comparisons between aware and naive :class:`.datetime` instances don't raise :exc:`TypeError`. .. versionchanged:: 3.13 Comparison between :class:`.datetime` object and an instance of the :class:`date` subclass that is not a :class:`!datetime` subclass no longer converts the latter to :class:`!date`, ignoring the time part and the time zone. The default behavior can be changed by overriding the special comparison methods in subclasses. Instance methods: .. method:: datetime.date() Return :class:`date` object with same year, month and day. .. method:: datetime.time() Return :class:`.time` object with same hour, minute, second, microsecond and fold. :attr:`.tzinfo` is ``None``. See also method :meth:`timetz`. .. versionchanged:: 3.6 The fold value is copied to the returned :class:`.time` object. .. method:: datetime.timetz() Return :class:`.time` object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method :meth:`time`. .. versionchanged:: 3.6 The fold value is copied to the returned :class:`.time` object. .. method:: datetime.replace(year=self.year, month=self.month, day=self.day, \ hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, \ tzinfo=self.tzinfo, *, fold=0) Return a new :class:`datetime` object with the same attributes, but with specified parameters updated. Note that ``tzinfo=None`` can be specified to create a naive datetime from an aware datetime with no conversion of date and time data. :class:`.datetime` objects are also supported by generic function :func:`copy.replace`. .. versionchanged:: 3.6 Added the *fold* parameter. .. method:: datetime.astimezone(tz=None) Return a :class:`.datetime` object with new :attr:`.tzinfo` attribute *tz*, adjusting the date and time data so the result is the same UTC time as *self*, but in *tz*'s local time. If provided, *tz* must be an instance of a :class:`tzinfo` subclass, and its :meth:`utcoffset` and :meth:`dst` methods must not return ``None``. If *self* is naive, it is presumed to represent time in the system time zone. If called without arguments (or with ``tz=None``) the system local time zone is assumed for the target time zone. The ``.tzinfo`` attribute of the converted datetime instance will be set to an instance of :class:`timezone` with the zone name and offset obtained from the OS. If ``self.tzinfo`` is *tz*, ``self.astimezone(tz)`` is equal to *self*: no adjustment of date or time data is performed. Else the result is local time in the time zone *tz*, representing the same UTC time as *self*: after ``astz = dt.astimezone(tz)``, ``astz - astz.utcoffset()`` will have the same date and time data as ``dt - dt.utcoffset()``. If you merely want to attach a :class:`timezone` object *tz* to a datetime *dt* without adjustment of date and time data, use ``dt.replace(tzinfo=tz)``. If you merely want to remove the :class:`!timezone` object from an aware datetime *dt* without conversion of date and time data, use ``dt.replace(tzinfo=None)``. Note that the default :meth:`tzinfo.fromutc` method can be overridden in a :class:`tzinfo` subclass to affect the result returned by :meth:`astimezone`. Ignoring error cases, :meth:`astimezone` acts like:: def astimezone(self, tz): if self.tzinfo is tz: return self # Convert self to UTC, and attach the new timezone object. utc = (self - self.utcoffset()).replace(tzinfo=tz) # Convert from UTC to tz's local time. return tz.fromutc(utc) .. versionchanged:: 3.3 *tz* now can be omitted. .. versionchanged:: 3.6 The :meth:`astimezone` method can now be called on naive instances that are presumed to represent system local time. .. method:: datetime.utcoffset() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.utcoffset(self)``, and raises an exception if the latter doesn't return ``None`` or a :class:`timedelta` object with magnitude less than one day. .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. method:: datetime.dst() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.dst(self)``, and raises an exception if the latter doesn't return ``None`` or a :class:`timedelta` object with magnitude less than one day. .. versionchanged:: 3.7 The DST offset is not restricted to a whole number of minutes. .. method:: datetime.tzname() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.tzname(self)``, raises an exception if the latter doesn't return ``None`` or a string object, .. method:: datetime.timetuple() Return a :class:`time.struct_time` such as returned by :func:`time.localtime`. ``d.timetuple()`` is equivalent to:: time.struct_time((d.year, d.month, d.day, d.hour, d.minute, d.second, d.weekday(), yday, dst)) where ``yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1`` is the day number within the current year starting with 1 for January 1st. The :attr:`~time.struct_time.tm_isdst` flag of the result is set according to the :meth:`dst` method: :attr:`.tzinfo` is ``None`` or :meth:`dst` returns ``None``, :attr:`!tm_isdst` is set to ``-1``; else if :meth:`dst` returns a non-zero value, :attr:`!tm_isdst` is set to 1; else :attr:`!tm_isdst` is set to 0. .. method:: datetime.utctimetuple() If :class:`.datetime` instance ``d`` is naive, this is the same as ``d.timetuple()`` except that :attr:`~.time.struct_time.tm_isdst` is forced to 0 regardless of what ``d.dst()`` returns. DST is never in effect for a UTC time. If ``d`` is aware, ``d`` is normalized to UTC time, by subtracting ``d.utcoffset()``, and a :class:`time.struct_time` for the normalized time is returned. :attr:`!tm_isdst` is forced to 0. Note that an :exc:`OverflowError` may be raised if ``d.year`` was ``MINYEAR`` or ``MAXYEAR`` and UTC adjustment spills over a year boundary. .. warning:: Because naive ``datetime`` objects are treated by many ``datetime`` methods as local times, it is preferred to use aware datetimes to represent times in UTC; as a result, using :meth:`datetime.utctimetuple` may give misleading results. If you have a naive ``datetime`` representing UTC, use ``datetime.replace(tzinfo=timezone.utc)`` to make it aware, at which point you can use :meth:`.datetime.timetuple`. .. method:: datetime.toordinal() Return the proleptic Gregorian ordinal of the date. The same as ``self.date().toordinal()``. .. method:: datetime.timestamp() Return POSIX timestamp corresponding to the :class:`.datetime` instance. The return value is a :class:`float` similar to that returned by :func:`time.time`. Naive :class:`.datetime` instances are assumed to represent local time and this method relies on platform C functions to perform the conversion. Since :class:`!datetime` supports a wider range of values than the platform C functions on many platforms, this method may raise :exc:`OverflowError` or :exc:`OSError` for times far in the past or far in the future. For aware :class:`.datetime` instances, the return value is computed as:: (dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds() .. note:: There is no method to obtain the POSIX timestamp directly from a naive :class:`.datetime` instance representing UTC time. If your application uses this convention and your system time zone is not set to UTC, you can obtain the POSIX timestamp by supplying ``tzinfo=timezone.utc``:: timestamp = dt.replace(tzinfo=timezone.utc).timestamp() or by calculating the timestamp directly:: timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1) .. versionadded:: 3.3 .. versionchanged:: 3.6 The :meth:`timestamp` method uses the :attr:`.fold` attribute to disambiguate the times during a repeated interval. .. versionchanged:: 3.6 This method no longer relies on the platform C :c:func:`mktime` function to perform conversions. .. method:: datetime.weekday() Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as ``self.date().weekday()``. See also :meth:`isoweekday`. .. method:: datetime.isoweekday() Return the day of the week as an integer, where Monday is 1 and Sunday is 7. The same as ``self.date().isoweekday()``. See also :meth:`weekday`, :meth:`isocalendar`. .. method:: datetime.isocalendar() Return a :term:`named tuple` with three components: ``year``, ``week`` and ``weekday``. The same as ``self.date().isocalendar()``. .. method:: datetime.isoformat(sep='T', timespec='auto') Return a string representing the date and time in ISO 8601 format: - ``YYYY-MM-DDTHH:MM:SS.ffffff``, if :attr:`microsecond` is not 0 - ``YYYY-MM-DDTHH:MM:SS``, if :attr:`microsecond` is 0 If :meth:`utcoffset` does not return ``None``, a string is appended, giving the UTC offset: - ``YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond` is not 0 - ``YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond` is 0 Examples:: >>> import datetime as dt >>> dt.datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat() '2019-05-18T15:17:08.132263' >>> dt.datetime(2019, 5, 18, 15, 17, tzinfo=dt.timezone.utc).isoformat() '2019-05-18T15:17:00+00:00' The optional argument *sep* (default ``'T'``) is a one-character separator, placed between the date and time portions of the result. For example:: >>> import datetime as dt >>> class TZ(dt.tzinfo): ... """A time zone with an arbitrary, constant -06:39 offset.""" ... def utcoffset(self, when): ... return dt.timedelta(hours=-6, minutes=-39) ... >>> dt.datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ') '2002-12-25 00:00:00-06:39' >>> dt.datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat() '2009-11-27T00:00:00.000100-06:39' The optional argument *timespec* specifies the number of additional components of the time to include (the default is ``'auto'``). It can be one of the following: - ``'auto'``: Same as ``'seconds'`` if :attr:`microsecond` is 0, same as ``'microseconds'`` otherwise. - ``'hours'``: Include the :attr:`hour` in the two-digit ``HH`` format. - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in ``HH:MM`` format. - ``'seconds'``: Include :attr:`hour`, :attr:`minute`, and :attr:`second` in ``HH:MM:SS`` format. - ``'milliseconds'``: Include full time, but truncate fractional second part to milliseconds. ``HH:MM:SS.sss`` format. - ``'microseconds'``: Include full time in ``HH:MM:SS.ffffff`` format. .. note:: Excluded time components are truncated, not rounded. :exc:`ValueError` will be raised on an invalid *timespec* argument:: >>> import datetime as dt >>> dt.datetime.now().isoformat(timespec='minutes') # doctest: +SKIP '2002-12-25T00:00' >>> my_datetime = dt.datetime(2015, 1, 1, 12, 30, 59, 0) >>> my_datetime.isoformat(timespec='microseconds') '2015-01-01T12:30:59.000000' .. versionchanged:: 3.6 Added the *timespec* parameter. .. method:: datetime.__str__() For a :class:`.datetime` instance ``d``, ``str(d)`` is equivalent to ``d.isoformat(' ')``. .. method:: datetime.ctime() Return a string representing the date and time:: >>> import datetime as dt >>> dt.datetime(2002, 12, 4, 20, 30, 40).ctime() 'Wed Dec 4 20:30:40 2002' The output string will *not* include time zone information, regardless of whether the input is aware or naive. ``d.ctime()`` is equivalent to:: time.ctime(time.mktime(d.timetuple())) on platforms where the native C :c:func:`ctime` function (which :func:`time.ctime` invokes, but which :meth:`datetime.ctime` does not invoke) conforms to the C standard. .. method:: datetime.strftime(format) Return a string representing the date and time, controlled by an explicit format string. See also :ref:`strftime-strptime-behavior` and :meth:`datetime.isoformat`. .. method:: datetime.__format__(format) Same as :meth:`.datetime.strftime`. This makes it possible to specify a format string for a :class:`.datetime` object in :ref:`formatted string literals <f-strings>` and when using :meth:`str.format`. See also :ref:`strftime-strptime-behavior` and :meth:`datetime.isoformat`. Examples of usage: :class:`!datetime` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Examples of working with :class:`.datetime` objects: .. doctest:: >>> import datetime as dt >>> # Using datetime.combine() >>> d = dt.date(2005, 7, 14) >>> t = dt.time(12, 30) >>> dt.datetime.combine(d, t) datetime.datetime(2005, 7, 14, 12, 30) >>> # Using datetime.now() >>> dt.datetime.now() # doctest: +SKIP datetime.datetime(2007, 12, 6, 16, 29, 43, 79043) # GMT +1 >>> dt.datetime.now(dt.timezone.utc) # doctest: +SKIP datetime.datetime(2007, 12, 6, 15, 29, 43, 79060, tzinfo=datetime.timezone.utc) >>> # Using datetime.strptime() >>> my_datetime = dt.datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M") >>> my_datetime datetime.datetime(2006, 11, 21, 16, 30) >>> # Using datetime.timetuple() to get tuple of all attributes >>> tt = my_datetime.timetuple() >>> for it in tt: # doctest: +SKIP ... print(it) ... 2006 # year 11 # month 21 # day 16 # hour 30 # minute 0 # second 1 # weekday (0 = Monday) 325 # number of days since 1st January -1 # dst - method tzinfo.dst() returned None >>> # Date in ISO format >>> ic = my_datetime.isocalendar() >>> for it in ic: # doctest: +SKIP ... print(it) ... 2006 # ISO year 47 # ISO week 2 # ISO weekday >>> # Formatting a datetime >>> my_datetime.strftime("%A, %d. %B %Y %I:%M%p") 'Tuesday, 21. November 2006 04:30PM' >>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(my_datetime, "day", "month", "time") 'The day is 21, the month is November, the time is 04:30PM.' The example below defines a :class:`tzinfo` subclass capturing time zone information for Kabul, Afghanistan, which used +4 UTC until 1945 and then +4:30 UTC thereafter:: import datetime as dt class KabulTz(dt.tzinfo): # Kabul used +4 until 1945, when they moved to +4:30 UTC_MOVE_DATE = dt.datetime(1944, 12, 31, 20, tzinfo=dt.timezone.utc) def utcoffset(self, when): if when.year < 1945: return dt.timedelta(hours=4) elif (1945, 1, 1, 0, 0) <= when.timetuple()[:5] < (1945, 1, 1, 0, 30): # An ambiguous ("imaginary") half-hour range representing # a 'fold' in time due to the shift from +4 to +4:30. # If when falls in the imaginary range, use fold to decide how # to resolve. See PEP 495. return dt.timedelta(hours=4, minutes=(30 if when.fold else 0)) else: return dt.timedelta(hours=4, minutes=30) def fromutc(self, when): # Follow same validations as in datetime.tzinfo if not isinstance(when, dt.datetime): raise TypeError("fromutc() requires a datetime argument") if when.tzinfo is not self: raise ValueError("when.tzinfo is not self") # A custom implementation is required for fromutc as # the input to this function is a datetime with utc values # but with a tzinfo set to self. # See datetime.astimezone or fromtimestamp. if when.replace(tzinfo=dt.timezone.utc) >= self.UTC_MOVE_DATE: return when + dt.timedelta(hours=4, minutes=30) else: return when + dt.timedelta(hours=4) def dst(self, when): # Kabul does not observe daylight saving time. return dt.timedelta(0) def tzname(self, when): if when >= self.UTC_MOVE_DATE: return "+04:30" return "+04" Usage of ``KabulTz`` from above:: >>> tz1 = KabulTz() >>> # Datetime before the change >>> dt1 = dt.datetime(1900, 11, 21, 16, 30, tzinfo=tz1) >>> print(dt1.utcoffset()) 4:00:00 >>> # Datetime after the change >>> dt2 = dt.datetime(2006, 6, 14, 13, 0, tzinfo=tz1) >>> print(dt2.utcoffset()) 4:30:00 >>> # Convert datetime to another time zone >>> dt3 = dt2.astimezone(dt.timezone.utc) >>> dt3 datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc) >>> dt2 datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz()) >>> dt2 == dt3 True .. _datetime-time: :class:`!time` objects ---------------------- A :class:`.time` object represents a (local) time of day, independent of any particular day, and subject to adjustment via a :class:`tzinfo` object. .. class:: time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0) All arguments are optional. *tzinfo* may be ``None``, or an instance of a :class:`tzinfo` subclass. The remaining arguments must be integers in the following ranges: * ``0 <= hour < 24``, * ``0 <= minute < 60``, * ``0 <= second < 60``, * ``0 <= microsecond < 1000000``, * ``fold in [0, 1]``. If an argument outside those ranges is given, :exc:`ValueError` is raised. All default to 0 except *tzinfo*, which defaults to ``None``. Class attributes: .. attribute:: time.min The earliest representable :class:`.time`, ``time(0, 0, 0, 0)``. .. attribute:: time.max The latest representable :class:`.time`, ``time(23, 59, 59, 999999)``. .. attribute:: time.resolution The smallest possible difference between non-equal :class:`.time` objects, ``timedelta(microseconds=1)``, although note that arithmetic on :class:`.time` objects is not supported. Instance attributes (read-only): .. attribute:: time.hour In ``range(24)``. .. attribute:: time.minute In ``range(60)``. .. attribute:: time.second In ``range(60)``. .. attribute:: time.microsecond In ``range(1000000)``. .. attribute:: time.tzinfo The object passed as the tzinfo argument to the :class:`.time` constructor, or ``None`` if none was passed. .. attribute:: time.fold In ``[0, 1]``. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The values 0 and 1 represent, respectively, the earlier and later of the two moments with the same wall time representation. .. versionadded:: 3.6 :class:`.time` objects support equality and order comparisons, where ``a`` is considered less than ``b`` when ``a`` precedes ``b`` in time. Naive and aware :class:`!time` objects are never equal. Order comparison between naive and aware :class:`!time` objects raises :exc:`TypeError`. If both comparands are aware, and have the same :attr:`~.time.tzinfo` attribute, the :attr:`!tzinfo` and :attr:`!fold` attributes are ignored and the base times are compared. If both comparands are aware and have different :attr:`!tzinfo` attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from ``self.utcoffset()``). .. versionchanged:: 3.3 Equality comparisons between aware and naive :class:`.time` instances don't raise :exc:`TypeError`. In Boolean contexts, a :class:`.time` object is always considered to be true. .. versionchanged:: 3.5 Before Python 3.5, a :class:`.time` object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See :issue:`13936` for more information. Other constructors: .. classmethod:: time.fromisoformat(time_string) Return a :class:`.time` corresponding to a *time_string* in any valid ISO 8601 format, with the following exceptions: 1. Time zone offsets may have fractional seconds. 2. The leading ``T``, normally required in cases where there may be ambiguity between a date and a time, is not required. 3. Fractional seconds may have any number of digits (anything beyond 6 will be truncated). 4. Fractional hours and minutes are not supported. Examples: .. doctest:: >>> import datetime as dt >>> dt.time.fromisoformat('04:23:01') datetime.time(4, 23, 1) >>> dt.time.fromisoformat('T04:23:01') datetime.time(4, 23, 1) >>> dt.time.fromisoformat('T042301') datetime.time(4, 23, 1) >>> dt.time.fromisoformat('04:23:01.000384') datetime.time(4, 23, 1, 384) >>> dt.time.fromisoformat('04:23:01,000384') datetime.time(4, 23, 1, 384) >>> dt.time.fromisoformat('04:23:01+04:00') datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400))) >>> dt.time.fromisoformat('04:23:01Z') datetime.time(4, 23, 1, tzinfo=datetime.timezone.utc) >>> dt.time.fromisoformat('04:23:01+00:00') datetime.time(4, 23, 1, tzinfo=datetime.timezone.utc) .. versionadded:: 3.7 .. versionchanged:: 3.11 Previously, this method only supported formats that could be emitted by :meth:`time.isoformat`. .. classmethod:: time.strptime(date_string, format) Return a :class:`.time` corresponding to *date_string*, parsed according to *format*. If *format* does not contain microseconds or timezone information, this is equivalent to:: time(*(time.strptime(date_string, format)[3:6])) :exc:`ValueError` is raised if the *date_string* and *format* cannot be parsed by :func:`time.strptime` or if it returns a value which is not a time tuple. See also :ref:`strftime-strptime-behavior` and :meth:`time.fromisoformat`. .. versionadded:: 3.14 Instance methods: .. method:: time.replace(hour=self.hour, minute=self.minute, second=self.second, \ microsecond=self.microsecond, tzinfo=self.tzinfo, *, fold=0) Return a new :class:`.time` with the same values, but with specified parameters updated. Note that ``tzinfo=None`` can be specified to create a naive :class:`!time` from an aware :class:`!time`, without conversion of the time data. :class:`.time` objects are also supported by generic function :func:`copy.replace`. .. versionchanged:: 3.6 Added the *fold* parameter. .. method:: time.isoformat(timespec='auto') Return a string representing the time in ISO 8601 format, one of: - ``HH:MM:SS.ffffff``, if :attr:`microsecond` is not 0 - ``HH:MM:SS``, if :attr:`microsecond` is 0 - ``HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]``, if :meth:`utcoffset` does not return ``None`` - ``HH:MM:SS+HH:MM[:SS[.ffffff]]``, if :attr:`microsecond` is 0 and :meth:`utcoffset` does not return ``None`` The optional argument *timespec* specifies the number of additional components of the time to include (the default is ``'auto'``). It can be one of the following: - ``'auto'``: Same as ``'seconds'`` if :attr:`microsecond` is 0, same as ``'microseconds'`` otherwise. - ``'hours'``: Include the :attr:`hour` in the two-digit ``HH`` format. - ``'minutes'``: Include :attr:`hour` and :attr:`minute` in ``HH:MM`` format. - ``'seconds'``: Include :attr:`hour`, :attr:`minute`, and :attr:`second` in ``HH:MM:SS`` format. - ``'milliseconds'``: Include full time, but truncate fractional second part to milliseconds. ``HH:MM:SS.sss`` format. - ``'microseconds'``: Include full time in ``HH:MM:SS.ffffff`` format. .. note:: Excluded time components are truncated, not rounded. :exc:`ValueError` will be raised on an invalid *timespec* argument. Example:: >>> import datetime as dt >>> dt.time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes') '12:34' >>> my_time = dt.time(hour=12, minute=34, second=56, microsecond=0) >>> my_time.isoformat(timespec='microseconds') '12:34:56.000000' >>> my_time.isoformat(timespec='auto') '12:34:56' .. versionchanged:: 3.6 Added the *timespec* parameter. .. method:: time.__str__() For a time ``t``, ``str(t)`` is equivalent to ``t.isoformat()``. .. method:: time.strftime(format) Return a string representing the time, controlled by an explicit format string. See also :ref:`strftime-strptime-behavior` and :meth:`time.isoformat`. .. method:: time.__format__(format) Same as :meth:`.time.strftime`. This makes it possible to specify a format string for a :class:`.time` object in :ref:`formatted string literals <f-strings>` and when using :meth:`str.format`. See also :ref:`strftime-strptime-behavior` and :meth:`time.isoformat`. .. method:: time.utcoffset() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.utcoffset(None)``, and raises an exception if the latter doesn't return ``None`` or a :class:`timedelta` object with magnitude less than one day. .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. method:: time.dst() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.dst(None)``, and raises an exception if the latter doesn't return ``None``, or a :class:`timedelta` object with magnitude less than one day. .. versionchanged:: 3.7 The DST offset is not restricted to a whole number of minutes. .. method:: time.tzname() If :attr:`.tzinfo` is ``None``, returns ``None``, else returns ``self.tzinfo.tzname(None)``, or raises an exception if the latter doesn't return ``None`` or a string object. Examples of usage: :class:`!time` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Examples of working with a :class:`.time` object:: >>> import datetime as dt >>> class TZ1(dt.tzinfo): ... def utcoffset(self, when): ... return dt.timedelta(hours=1) ... def dst(self, when): ... return dt.timedelta(0) ... def tzname(self, when): ... return "+01:00" ... def __repr__(self): ... return f"{self.__class__.__name__}()" ... >>> t = dt.time(12, 10, 30, tzinfo=TZ1()) >>> t datetime.time(12, 10, 30, tzinfo=TZ1()) >>> t.isoformat() '12:10:30+01:00' >>> t.dst() datetime.timedelta(0) >>> t.tzname() '+01:00' >>> t.strftime("%H:%M:%S %Z") '12:10:30 +01:00' >>> 'The {} is {:%H:%M}.'.format("time", t) 'The time is 12:10.' .. _datetime-tzinfo: :class:`!tzinfo` objects ------------------------ .. class:: tzinfo() This is an :term:`abstract base class`, meaning that this class should not be instantiated directly. Define a subclass of :class:`tzinfo` to capture information about a particular time zone. An instance of (a concrete subclass of) :class:`tzinfo` can be passed to the constructors for :class:`.datetime` and :class:`.time` objects. The latter objects view their attributes as being in local time, and the :class:`!tzinfo` object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them. You need to derive a concrete subclass, and (at least) supply implementations of the standard :class:`tzinfo` methods needed by the :class:`.datetime` methods you use. The :mod:`!datetime` module provides :class:`timezone`, a simple concrete subclass of :class:`!tzinfo` which can represent time zones with fixed offset from UTC such as UTC itself or North American EST and EDT. Special requirement for pickling: A :class:`tzinfo` subclass must have an :meth:`~object.__init__` method that can be called with no arguments, otherwise it can be pickled but possibly not unpickled again. This is a technical requirement that may be relaxed in the future. A concrete subclass of :class:`tzinfo` may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware :mod:`!datetime` objects. If in doubt, simply implement all of them. .. method:: tzinfo.utcoffset(dt) Return offset of local time from UTC, as a :class:`timedelta` object that is positive east of UTC. If local time is west of UTC, this should be negative. This represents the *total* offset from UTC; for example, if a :class:`tzinfo` object represents both time zone and DST adjustments, :meth:`utcoffset` should return their sum. If the UTC offset isn't known, return ``None``. Else the value returned must be a :class:`timedelta` object strictly between ``-timedelta(hours=24)`` and ``timedelta(hours=24)`` (the magnitude of the offset must be less than one day). Most implementations of :meth:`utcoffset` will probably look like one of these two:: return CONSTANT # fixed-offset class return CONSTANT + self.dst(dt) # daylight-aware class If :meth:`utcoffset` does not return ``None``, :meth:`dst` should not return ``None`` either. The default implementation of :meth:`utcoffset` raises :exc:`NotImplementedError`. .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. method:: tzinfo.dst(dt) Return the daylight saving time (DST) adjustment, as a :class:`timedelta` object or ``None`` if DST information isn't known. Return ``timedelta(0)`` if DST is not in effect. If DST is in effect, return the offset as a :class:`timedelta` object (see :meth:`utcoffset` for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by :meth:`utcoffset`, so there's no need to consult :meth:`dst` unless you're interested in obtaining DST info separately. For example, :meth:`datetime.timetuple` calls its :attr:`~.datetime.tzinfo` attribute's :meth:`dst` method to determine how the :attr:`~time.struct_time.tm_isdst` flag should be set, and :meth:`tzinfo.fromutc` calls :meth:`dst` to account for DST changes when crossing time zones. An instance *tz* of a :class:`tzinfo` subclass that models both standard and daylight times must be consistent in this sense: ``tz.utcoffset(dt) - tz.dst(dt)`` must return the same result for every :class:`.datetime` *dt* with ``dt.tzinfo == tz``. For sane :class:`!tzinfo` subclasses, this expression yields the time zone's "standard offset", which should not depend on the date or the time, but only on geographic location. The implementation of :meth:`datetime.astimezone` relies on this, but cannot detect violations; it's the programmer's responsibility to ensure it. If a :class:`!tzinfo` subclass cannot guarantee this, it may be able to override the default implementation of :meth:`tzinfo.fromutc` to work correctly with :meth:`~.datetime.astimezone` regardless. Most implementations of :meth:`dst` will probably look like one of these two:: import datetime as dt def dst(self, when): # a fixed-offset class: doesn't account for DST return dt.timedelta(0) or:: import datetime as dt def dst(self, when): # Code to set dston and dstoff to the time zone's DST # transition times based on the input when.year, and expressed # in standard local time. if dston <= when.replace(tzinfo=None) < dstoff: return dt.timedelta(hours=1) else: return dt.timedelta(0) The default implementation of :meth:`dst` raises :exc:`NotImplementedError`. .. versionchanged:: 3.7 The DST offset is not restricted to a whole number of minutes. .. method:: tzinfo.tzname(dt) Return the time zone name corresponding to the :class:`.datetime` object *dt*, as a string. Nothing about string names is defined by the :mod:`!datetime` module, and there's no requirement that it mean anything in particular. For example, ``"GMT"``, ``"UTC"``, ``"-500"``, ``"-5:00"``, ``"EDT"``, ``"US/Eastern"``, ``"America/New York"`` are all valid replies. Return ``None`` if a string name isn't known. Note that this is a method rather than a fixed string primarily because some :class:`tzinfo` subclasses will wish to return different names depending on the specific value of *dt* passed, especially if the :class:`!tzinfo` class is accounting for daylight time. The default implementation of :meth:`tzname` raises :exc:`NotImplementedError`. These methods are called by a :class:`.datetime` or :class:`.time` object, in response to their methods of the same names. A :class:`!datetime` object passes itself as the argument, and a :class:`!time` object passes ``None`` as the argument. A :class:`tzinfo` subclass's methods should therefore be prepared to accept a *dt* argument of ``None``, or of class :class:`!datetime`. When ``None`` is passed, it's up to the class designer to decide the best response. For example, returning ``None`` is appropriate if the class wishes to say that time objects don't participate in the :class:`tzinfo` protocols. It may be more useful for ``utcoffset(None)`` to return the standard UTC offset, as there is no other convention for discovering the standard offset. When a :class:`.datetime` object is passed in response to a :class:`!datetime` method, ``dt.tzinfo`` is the same object as *self*. :class:`tzinfo` methods can rely on this, unless user code calls :class:`!tzinfo` methods directly. The intent is that the :class:`!tzinfo` methods interpret *dt* as being in local time, and not need worry about objects in other time zones. There is one more :class:`tzinfo` method that a subclass may wish to override: .. method:: tzinfo.fromutc(dt) This is called from the default :meth:`datetime.astimezone` implementation. When called from that, ``dt.tzinfo`` is *self*, and *dt*'s date and time data are to be viewed as expressing a UTC time. The purpose of :meth:`fromutc` is to adjust the date and time data, returning an equivalent datetime in *self*'s local time. Most :class:`tzinfo` subclasses should be able to inherit the default :meth:`fromutc` implementation without problems. It's strong enough to handle fixed-offset time zones, and time zones accounting for both standard and daylight time, and the latter even if the DST transition times differ in different years. An example of a time zone the default :meth:`fromutc` implementation may not handle correctly in all cases is one where the standard offset (from UTC) depends on the specific date and time passed, which can happen for political reasons. The default implementations of :meth:`~.datetime.astimezone` and :meth:`fromutc` may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes. Skipping code for error cases, the default :meth:`fromutc` implementation acts like:: import datetime as dt def fromutc(self, when): # raise ValueError error if when.tzinfo is not self dtoff = when.utcoffset() dtdst = when.dst() # raise ValueError if dtoff is None or dtdst is None delta = dtoff - dtdst # this is self's standard offset if delta: when += delta # convert to standard local time dtdst = when.dst() # raise ValueError if dtdst is None if dtdst: return when + dtdst else: return when In the following :download:`tzinfo_examples.py <../includes/tzinfo_examples.py>` file there are some examples of :class:`tzinfo` classes: .. literalinclude:: ../includes/tzinfo_examples.py Note that there are unavoidable subtleties twice per year in a :class:`tzinfo` subclass accounting for both standard and daylight time, at the DST transition points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the minute after 1:59 (EST) on the second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November:: UTC 3:MM 4:MM 5:MM 6:MM 7:MM 8:MM EST 22:MM 23:MM 0:MM 1:MM 2:MM 3:MM EDT 23:MM 0:MM 1:MM 2:MM 3:MM 4:MM start 22:MM 23:MM 0:MM 1:MM 3:MM 4:MM end 23:MM 0:MM 1:MM 1:MM 2:MM 3:MM When DST starts (the "start" line), the local wall clock leaps from 1:59 to 3:00. A wall time of the form 2:MM doesn't really make sense on that day, so ``astimezone(Eastern)`` won't deliver a result with ``hour == 2`` on the day DST begins. For example, at the Spring forward transition of 2016, we get:: >>> import datetime as dt >>> from tzinfo_examples import HOUR, Eastern >>> u0 = dt.datetime(2016, 3, 13, 5, tzinfo=dt.timezone.utc) >>> for i in range(4): ... u = u0 + i*HOUR ... t = u.astimezone(Eastern) ... print(u.time(), 'UTC =', t.time(), t.tzname()) ... 05:00:00 UTC = 00:00:00 EST 06:00:00 UTC = 01:00:00 EST 07:00:00 UTC = 03:00:00 EDT 08:00:00 UTC = 04:00:00 EDT When DST ends (the "end" line), there's a potentially worse problem: there's an hour that can't be spelled unambiguously in local wall time: the last hour of daylight time. In Eastern, that's times of the form 5:MM UTC on the day daylight time ends. The local wall clock leaps from 1:59 (daylight time) back to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous. :meth:`~.datetime.astimezone` mimics the local clock's behavior by mapping two adjacent UTC hours into the same local hour then. In the Eastern example, UTC times of the form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times have the :attr:`~.datetime.fold` attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get:: >>> import datetime as dt >>> from tzinfo_examples import HOUR, Eastern >>> u0 = dt.datetime(2016, 11, 6, 4, tzinfo=dt.timezone.utc) >>> for i in range(4): ... u = u0 + i*HOUR ... t = u.astimezone(Eastern) ... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold) ... 04:00:00 UTC = 00:00:00 EDT 0 05:00:00 UTC = 01:00:00 EDT 0 06:00:00 UTC = 01:00:00 EST 1 07:00:00 UTC = 02:00:00 EST 0 Note that the :class:`.datetime` instances that differ only by the value of the :attr:`~.datetime.fold` attribute are considered equal in comparisons. Applications that can't bear wall-time ambiguities should explicitly check the value of the :attr:`~.datetime.fold` attribute or avoid using hybrid :class:`tzinfo` subclasses; there are no ambiguities when using :class:`timezone`, or any other fixed-offset :class:`!tzinfo` subclass (such as a class representing only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)). .. seealso:: :mod:`zoneinfo` The :mod:`!datetime` module has a basic :class:`timezone` class (for handling arbitrary fixed offsets from UTC) and its :attr:`timezone.utc` attribute (a UTC :class:`!timezone` instance). ``zoneinfo`` brings the *IANA time zone database* (also known as the Olson database) to Python, and its usage is recommended. `IANA time zone database <https://www.iana.org/time-zones>`_ The Time Zone Database (often called tz, tzdata or zoneinfo) contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules. .. _datetime-timezone: :class:`!timezone` objects -------------------------- The :class:`timezone` class is a subclass of :class:`tzinfo`, each instance of which represents a time zone defined by a fixed offset from UTC. Objects of this class cannot be used to represent time zone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time. .. class:: timezone(offset[, name]) The *offset* argument must be specified as a :class:`timedelta` object representing the difference between the local time and UTC. It must be strictly between ``-timedelta(hours=24)`` and ``timedelta(hours=24)``, otherwise :exc:`ValueError` is raised. The *name* argument is optional. If specified it must be a string that will be used as the value returned by the :meth:`datetime.tzname` method. .. versionadded:: 3.2 .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. method:: timezone.utcoffset(dt) Return the fixed value specified when the :class:`timezone` instance is constructed. The *dt* argument is ignored. The return value is a :class:`timedelta` instance equal to the difference between the local time and UTC. .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. method:: timezone.tzname(dt) Return the fixed value specified when the :class:`timezone` instance is constructed. If *name* is not provided in the constructor, the name returned by ``tzname(dt)`` is generated from the value of the ``offset`` as follows. If *offset* is ``timedelta(0)``, the name is "UTC", otherwise it is a string in the format ``UTC±HH:MM``, where ± is the sign of ``offset``, HH and MM are two digits of ``offset.hours`` and ``offset.minutes`` respectively. .. versionchanged:: 3.6 Name generated from ``offset=timedelta(0)`` is now plain ``'UTC'``, not ``'UTC+00:00'``. .. method:: timezone.dst(dt) Always returns ``None``. .. method:: timezone.fromutc(dt) Return ``dt + offset``. The *dt* argument must be an aware :class:`.datetime` instance, with ``tzinfo`` set to ``self``. Class attributes: .. attribute:: timezone.utc The UTC time zone, ``timezone(timedelta(0))``. .. index:: single: % (percent); datetime format .. _strftime-strptime-behavior: :meth:`!strftime` and :meth:`!strptime` behavior ------------------------------------------------ :class:`date`, :class:`.datetime`, and :class:`.time` objects all support a ``strftime(format)`` method, to create a string representing the time under the control of an explicit format string. Conversely, the :meth:`date.strptime`, :meth:`datetime.strptime` and :meth:`time.strptime` class methods create an object from a string representing the time and a corresponding format string. The table below provides a high-level comparison of :meth:`~.datetime.strftime` versus :meth:`~.datetime.strptime`: +----------------+--------------------------------------------------------+------------------------------------------------------------+ | | ``strftime`` | ``strptime`` | +================+========================================================+============================================================+ | Usage | Convert object to a string according to a given format | Parse a string into an object given a corresponding format | +----------------+--------------------------------------------------------+------------------------------------------------------------+ | Type of method | Instance method | Class method | +----------------+--------------------------------------------------------+------------------------------------------------------------+ | Signature | ``strftime(format)`` | ``strptime(date_string, format)`` | +----------------+--------------------------------------------------------+------------------------------------------------------------+ .. _format-codes: :meth:`!strftime` and :meth:`!strptime` format codes ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ These methods accept format codes that can be used to parse and format dates:: >>> import datetime as dt >>> dt.datetime.strptime('31/01/22 23:59:59.999999', ... '%d/%m/%y %H:%M:%S.%f') datetime.datetime(2022, 1, 31, 23, 59, 59, 999999) >>> _.strftime('%a %d %b %Y, %I:%M%p') 'Mon 31 Jan 2022, 11:59PM' The following is a list of all the format codes that the 2011 C standard requires, and these work on all supported platforms. +-----------+--------------------------------+------------------------+-------+ | Directive | Meaning | Example | Notes | | | | | | +===========+================================+========================+=======+ | ``%a`` | Weekday as locale's || Sun, Mon, ..., Sat | \(1) | | | abbreviated name. | (en_US); | | | | || So, Mo, ..., Sa | | | | | (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%A`` | Weekday as locale's full name. || Sunday, Monday, ..., | \(1) | | | | Saturday (en_US); | | | | || Sonntag, Montag, ..., | | | | | Samstag (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%b`` | Month as locale's abbreviated || Jan, Feb, ..., Dec | \(1) | | | name. | (en_US); | | | | || Jan, Feb, ..., Dez | | | | | (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%B`` | Month as locale's full name. || January, February, | \(1) | | | | ..., December (en_US);| | | | || Januar, Februar, ..., | | | | | Dezember (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%c`` | Locale's appropriate date and || Tue Aug 16 21:30:00 | \(1) | | | time representation. | 1988 (en_US); | | | | || Di 16 Aug 21:30:00 | | | | | 1988 (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%C`` | The year divided by 100 and | 01, 02, ..., 99 | \(0) | | | truncated to an integer as a | | | | | zero-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%d`` | Day of the month as a | 01, 02, ..., 31 | \(9), | | | zero-padded decimal number. | | \(10) | +-----------+--------------------------------+------------------------+-------+ | ``%D`` | Equivalent to ``%m/%d/%y``. | 11/28/25 | \(9) | | | | | | +-----------+--------------------------------+------------------------+-------+ | ``%e`` | The day of the month as a | ␣1, ␣2, ..., 31 | \(10) | | | space-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%F`` | Equivalent to ``%Y-%m-%d``, | 2025-10-11, | | | | the ISO 8601 format. | 1001-12-30 | | +-----------+--------------------------------+------------------------+-------+ | ``%g`` | Last 2 digits of ISO 8601 year | 00, 01, ..., 99 | \(0) | | | representing the year that | | | | | contains the greater part of | | | | | the ISO week (``%V``). | | | +-----------+--------------------------------+------------------------+-------+ | ``%G`` | ISO 8601 year with century | 0001, 0002, ..., 2013, | \(8) | | | representing the year that | 2014, ..., 9998, 9999 | | | | contains the greater part of | | | | | the ISO week (``%V``). | | | +-----------+--------------------------------+------------------------+-------+ | ``%h`` | Equivalent to ``%b``. | See ``%b``. | \(0) | +-----------+--------------------------------+------------------------+-------+ | ``%H`` | Hour (24-hour clock) as a | 00, 01, ..., 23 | \(9) | | | zero-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%I`` | Hour (12-hour clock) as a | 01, 02, ..., 12 | \(9) | | | zero-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%j`` | Day of the year as a | 001, 002, ..., 366 | \(9) | | | zero-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%m`` | Month as a zero-padded | 01, 02, ..., 12 | \(9) | | | decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%M`` | Minute as a zero-padded | 00, 01, ..., 59 | \(9) | | | decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%n`` | The newline character | ``\n`` | | | | (``'\n'``). For | | | | | :meth:`!strptime`, zero or | | | | | more whitespace. | | | +-----------+--------------------------------+------------------------+-------+ | ``%p`` | Locale's equivalent of either || AM, PM (en_US); | \(1), | | | AM or PM. || am, pm (de_DE) | \(3) | +-----------+--------------------------------+------------------------+-------+ | ``%r`` | Locale's 12-hour clock time. | 12:00:00 AM | \(1), | | | | | \(0) | +-----------+--------------------------------+------------------------+-------+ | ``%R`` | Equivalent to ``%H:%M``. | 10:01 | | +-----------+--------------------------------+------------------------+-------+ | ``%S`` | Second as a zero-padded | 00, 01, ..., 59 | \(4), | | | decimal number. | | \(9) | +-----------+--------------------------------+------------------------+-------+ | ``%t`` | The tab character (``'\t'``). | ``\t`` | | | | For :meth:`!strptime`, | | | | | zero or more whitespace. | | | +-----------+--------------------------------+------------------------+-------+ | ``%T`` | ISO 8601 time format, | 10:01:59 | | | | equivalent to ``%H:%M:%S``. | | | +-----------+--------------------------------+------------------------+-------+ | ``%u`` | ISO 8601 weekday as a decimal | 1, 2, ..., 7 | | | | number where 1 is Monday. | | | +-----------+--------------------------------+------------------------+-------+ | ``%U`` | Week number of the year | 00, 01, ..., 53 | \(7), | | | (Sunday as the first day of | | \(9) | | | the week) as a zero-padded | | | | | decimal number. All days in a | | | | | new year preceding the first | | | | | Sunday are considered to be in | | | | | week 0. | | | +-----------+--------------------------------+------------------------+-------+ | ``%V`` | ISO 8601 week as a decimal | 01, 02, ..., 53 | \(8), | | | number with Monday as | | \(9) | | | the first day of the week. | | | | | Week 01 is the week containing | | | | | Jan 4. | | | +-----------+--------------------------------+------------------------+-------+ | ``%w`` | Weekday as a decimal number, | 0, 1, ..., 6 | | | | where 0 is Sunday and 6 is | | | | | Saturday. | | | +-----------+--------------------------------+------------------------+-------+ | ``%W`` | Week number of the year | 00, 01, ..., 53 | \(7), | | | (Monday as the first day of | | \(9) | | | the week) as a zero-padded | | | | | decimal number. All days in a | | | | | new year preceding the first | | | | | Monday are considered to be in | | | | | week 0. | | | +-----------+--------------------------------+------------------------+-------+ | ``%x`` | Locale's appropriate date || 08/16/88 (None); | \(1) | | | representation. || 08/16/1988 (en_US); | | | | || 16.08.1988 (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%X`` | Locale's appropriate time || 21:30:00 (en_US); | \(1) | | | representation. || 21:30:00 (de_DE) | | +-----------+--------------------------------+------------------------+-------+ | ``%y`` | Year without century as a | 00, 01, ..., 99 | \(9) | | | zero-padded decimal number. | | | +-----------+--------------------------------+------------------------+-------+ | ``%Y`` | Year with century as a decimal | 0001, 0002, ..., 2013, | \(2) | | | number. | 2014, ..., 9998, 9999 | | +-----------+--------------------------------+------------------------+-------+ | ``%z`` | UTC offset in the form | (empty), +0000, | \(6) | | | ``±HHMM[SS[.ffffff]]`` (empty | -0400, +1030, | | | | string if the object is | +063415, | | | | naive). | -030712.345216 | | +-----------+--------------------------------+------------------------+-------+ | ``%Z`` | Time zone name (empty string | (empty), UTC, GMT | \(6) | | | if the object is naive). | | | +-----------+--------------------------------+------------------------+-------+ | ``%%`` | A literal ``'%'`` character. | % | | +-----------+--------------------------------+------------------------+-------+ The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling :meth:`~.datetime.strptime` with incomplete or ambiguous ISO 8601 directives will raise a :exc:`ValueError`. Several additional directives not required by the C11 standard are included for convenience. +-----------+--------------------------------+------------------------+-------+ | Directive | Meaning | Example | Notes | +===========+================================+========================+=======+ | ``%f`` | Microsecond as a decimal | 000000, 000001, ..., | \(5) | | | number, zero-padded to 6 | 999999 | | | | digits. | | | +-----------+--------------------------------+------------------------+-------+ | ``%:z`` | UTC offset in the form | (empty), +00:00, | \(6) | | | ``±HH:MM[:SS[.ffffff]]`` | -04:00, +10:30, | | | | (empty string if the object is | +06:34:15, | | | | naive). | -03:07:12.345216 | | +-----------+--------------------------------+------------------------+-------+ The full set of format codes supported varies across platforms, because Python calls the platform C library's :c:func:`strftime` function, and platform variations are common. To see the full set of format codes supported on your platform, consult the :manpage:`strftime(3)` documentation. There are also differences between platforms in handling of unsupported format specifiers. .. versionadded:: 3.6 ``%G``, ``%u`` and ``%V`` were added. .. versionadded:: 3.12 ``%:z`` was added for :meth:`~.datetime.strftime`. .. versionadded:: 3.15 ``%D``, ``%F``, ``%n``, ``%t``, and ``%:z`` were added for :meth:`~.datetime.strptime`. Technical detail ^^^^^^^^^^^^^^^^ Broadly speaking, ``d.strftime(fmt)`` acts like the :mod:`time` module's ``time.strftime(fmt, d.timetuple())`` although not all objects support a :meth:`~date.timetuple` method. For the :meth:`.datetime.strptime` and :meth:`.date.strptime` class methods, the default value is ``1900-01-01T00:00:00.000``: any components not specified in the format string will be pulled from the default value. .. note:: Format strings without separators can be ambiguous for parsing. For example, with ``%Y%m%d``, the string ``2026111`` may be parsed either as ``2026-11-01`` or as ``2026-01-11``. Use separators to ensure the input is parsed as intended. .. note:: When used to parse partial dates lacking a year, :meth:`.datetime.strptime` and :meth:`.date.strptime` will raise when encountering February 29 because the default year of 1900 is *not* a leap year. Always add a default leap year to partial date strings before parsing. .. testsetup:: # doctest seems to turn the warning into an error which makes it # show up and require matching and prevents the actual interesting # exception from being raised. # Manually apply the catch_warnings context manager import warnings catch_warnings = warnings.catch_warnings() catch_warnings.__enter__() warnings.simplefilter("ignore") .. testcleanup:: catch_warnings.__exit__() .. doctest:: >>> import datetime as dt >>> value = "2/29" >>> dt.datetime.strptime(value, "%m/%d") Traceback (most recent call last): ... ValueError: day 29 must be in range 1..28 for month 2 in year 1900 >>> dt.datetime.strptime(f"1904 {value}", "%Y %m/%d") datetime.datetime(1904, 2, 29, 0, 0) Using ``datetime.strptime(date_string, format)`` is equivalent to:: datetime(*(time.strptime(date_string, format)[0:6])) except when the format includes sub-second components or time zone offset information, which are supported in ``datetime.strptime`` but are discarded by ``time.strptime``. For :class:`.time` objects, the format codes for year, month, and day should not be used, as :class:`!time` objects have no such values. If they're used anyway, 1900 is substituted for the year, and 1 for the month and day. For :class:`date` objects, the format codes for hours, minutes, seconds, and microseconds should not be used, as :class:`date` objects have no such values. If they're used anyway, 0 is substituted for them. For the same reason, handling of format strings containing Unicode code points that can't be represented in the charset of the current locale is also platform-dependent. On some platforms such code points are preserved intact in the output, while on others ``strftime`` may raise :exc:`UnicodeError` or return an empty string instead. Notes: (0) This format code is currently unsupported by :meth:`~.datetime.strptime`. (1) Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, "month/day/year" versus "day/month/year"), and the output may contain non-ASCII characters. (2) The :meth:`~.datetime.strptime` method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width. .. versionchanged:: 3.2 In previous versions, :meth:`~.datetime.strftime` method was restricted to years >= 1900. .. versionchanged:: 3.3 In version 3.2, :meth:`~.datetime.strftime` method was restricted to years >= 1000. (3) When used with the :meth:`~.datetime.strptime` method, the ``%p`` directive only affects the output hour field if the ``%I`` directive is used to parse the hour. (4) Unlike the :mod:`time` module, the :mod:`!datetime` module does not support leap seconds. (5) When used with the :meth:`~.datetime.strptime` method, the ``%f`` directive accepts from one to six digits and zero pads on the right. ``%f`` is an extension to the set of format characters in the C standard (but implemented separately in datetime objects, and therefore always available). (6) For a naive object, the ``%z``, ``%:z`` and ``%Z`` format codes are replaced by empty strings. For an aware object: ``%z`` :meth:`~.datetime.utcoffset` is transformed into a string of the form ``±HHMM[SS[.ffffff]]``, where ``HH`` is a 2-digit string giving the number of UTC offset hours, ``MM`` is a 2-digit string giving the number of UTC offset minutes, ``SS`` is a 2-digit string giving the number of UTC offset seconds and ``ffffff`` is a 6-digit string giving the number of UTC offset microseconds. The ``ffffff`` part is omitted when the offset is a whole number of seconds and both the ``ffffff`` and the ``SS`` part is omitted when the offset is a whole number of minutes. For example, if :meth:`~.datetime.utcoffset` returns ``timedelta(hours=-3, minutes=-30)``, ``%z`` is replaced with the string ``'-0330'``. .. versionchanged:: 3.7 The UTC offset is not restricted to a whole number of minutes. .. versionchanged:: 3.7 When the ``%z`` directive is provided to the :meth:`~.datetime.strptime` method, the UTC offsets can have a colon as a separator between hours, minutes and seconds. For example, both ``'+010000'`` and ``'+01:00:00'`` will be parsed as an offset of one hour. In addition, providing ``'Z'`` is identical to ``'+00:00'``. ``%:z`` When used with :meth:`~.datetime.strftime`, behaves exactly as ``%z``, except that a colon separator is added between hours, minutes and seconds. When used with :meth:`~.datetime.strptime`, the UTC offset is *required* to have a colon as a separator between hours, minutes and seconds. For example, ``'+01:00:00'`` (but *not* ``'+010000'``) will be parsed as an offset of one hour. In addition, providing ``'Z'`` is identical to ``'+00:00'``. ``%Z`` In :meth:`~.datetime.strftime`, ``%Z`` is replaced by an empty string if :meth:`~.datetime.tzname` returns ``None``; otherwise ``%Z`` is replaced by the returned value, which must be a string. :meth:`~.datetime.strptime` only accepts certain values for ``%Z``: 1. any value in ``time.tzname`` for your machine's locale 2. the hard-coded values ``UTC`` and ``GMT`` So someone living in Japan may have ``JST``, ``UTC``, and ``GMT`` as valid values, but probably not ``EST``. It will raise ``ValueError`` for invalid values. .. versionchanged:: 3.2 When the ``%z`` directive is provided to the :meth:`~.datetime.strptime` method, an aware :class:`.datetime` object will be produced. The ``tzinfo`` of the result will be set to a :class:`timezone` instance. (7) When used with the :meth:`~.datetime.strptime` method, ``%U`` and ``%W`` are only used in calculations when the day of the week and the calendar year (``%Y``) are specified. (8) Similar to ``%U`` and ``%W``, ``%V`` is only used in calculations when the day of the week and the ISO year (``%G``) are specified in a :meth:`~.datetime.strptime` format string. Also note that ``%G`` and ``%Y`` are not interchangeable. (9) When used with the :meth:`~.datetime.strptime` method, the leading zero is optional for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``, ``%W``, and ``%V``. Format ``%y`` does require a leading zero. (10) When parsing a month and day using :meth:`~.datetime.strptime`, always include a year in the format. If the value you need to parse lacks a year, append an explicit dummy leap year. Otherwise your code will raise an exception when it encounters leap day because the default year used by the parser (1900) is not a leap year. Users run into that bug every leap year. .. doctest:: >>> month_day = "02/29" >>> dt.datetime.strptime(f"{month_day};1984", "%m/%d;%Y") # No leap year bug. datetime.datetime(1984, 2, 29, 0, 0) .. versionchanged:: 3.15 Using ``%d`` without a year now raises :exc:`ValueError`. .. deprecated-removed:: 3.15 3.17 :meth:`~.datetime.strptime` calls using a format string containing ``%e`` without a year now emit a :exc:`DeprecationWarning`. .. rubric:: Footnotes .. [#] If, that is, we ignore the effects of relativity. .. [#] This matches the definition of the "proleptic Gregorian" calendar in Dershowitz and Reingold's book *Calendrical Calculations*, where it's the base calendar for all computations. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems. .. [#] See R. H. van Gent's `guide to the mathematics of the ISO 8601 calendar <https://web.archive.org/web/20220531051136/https://webspace.science.uu.nl/~gent0113/calendar/isocalendar.htm>`_ for a good explanation.