* Copyright (C) 2016 and later: Unicode, Inc. and others.

* License & terms of use: http://www.unicode.org/copyright.html

**********************************************************************

* Copyright (c) 2003-2014, International Business Machines

* Corporation and others. All Rights Reserved.

**********************************************************************

* Author: Alan Liu

* Created: August 18 2003

* Since: ICU 2.8

**********************************************************************

Note: this directory currently contains tzcode as of tzcode2014b.tar.gz

with localtime.c patches from tzcode2014b.tar.gz

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OVERVIEW

This file describes the tools in icu/source/tools/tzcode

The purpose of these tools is to process the zoneinfo or "Olson" time

zone database into a form usable by ICU4C (release 2.8 and later).

Unlike earlier releases, ICU4C 2.8 supports historical time zone

behavior, as well as the full set of Olson compatibility IDs.

References:

ICU4C: https://icu.unicode.org/

Olson: ftp://ftp.iana.org/tz/releases/

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ICU4C vs. ICU4J

For ICU releases >= 2.8, both ICU4C and ICU4J implement full

historical time zones, based on Olson data. The implementations in C

and Java are somewhat different. The C implementation is a

self-contained implementation, whereas ICU4J uses the underlying JDK

1.3 or 1.4 time zone implementation.

Older versions of ICU (C and Java <= 2.6) implement a "present day

snapshot". This only reflects current time zone behavior, without

historical variation. Furthermore, it lacks the full set of Olson

compatibility IDs.

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BACKGROUND

The zoneinfo or "Olson" time zone package is used by various systems

to describe the behavior of time zones. The package consists of

several parts. E.g.:

Index of ftp://ftp.iana.org/tz/releases/

tzcode2014b.tar.gz 172 KB 3/25/2014 05:11:00 AM

tzdata2014b.tar.gz 216 KB 3/25/2014 05:11:00 AM

ICU only uses the tzdataYYYYV.tar.gz files,

where YYYY is the year and V is the version letter ('a'...'z').

This directory has partial contents of tzcode checked into ICU

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HOWTO

0. Note, these instructions will only work on POSIX type systems.

1. Obtain the current versions of tzdataYYYYV.tar.gz (aka `tzdata') from

the FTP site given above. Either manually download or use wget:

$ cd {path_to}/icu/source/tools/tzcode

$ wget "ftp://ftp.iana.org/tz/releases/tzdata*.tar.gz"

2. Copy only one tzdata*.tar.gz file into the icu/source/tools/tzcode/

directory (this directory).

*** Make sure you only have ONE FILE named tzdata*.tar.gz in the

directory.

3. Build ICU normally. You will see a notice "updating zoneinfo.txt..."

### Following instructions for ICU maintainers only ###

4. Obtain the current version of tzcodeYYYY.tar.gz from the FTP site to

this directory.

5. Run make target "check-dump". This target extract makes the original

tzcode and compile the original tzdata with icu supplemental data

(icuzones). Then it makes zdump / icuzdump and dump all time

transitions for all ICU timezone to files under zdumpout / icuzdumpout

directory. When they produce different results, the target returns

the error.

6. Don't forget to check in the new zoneinfo64.txt (from its location at

{path_to}/icu/source/data/misc/zoneinfo64.txt) into SVN.