| tz-link.html (46c599340f187db577b9212ab18022f3c7380c68) | tz-link.html (a979394afeb5c20fc58c5f5b005d51eb8f92f666) |
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| 1<!DOCTYPE html> 2<html lang="en"> 3<head> 4<title>Time zone and daylight saving time data</title> 5<meta charset="UTF-8"> 6<style> 7pre {margin-left: 2em; white-space: pre-wrap;} 8</style> --- 67 unchanged lines hidden (view full) --- 76<abbr title="GNU's Not Unix">GNU</abbr> 77C Library</a> (used in 78<a href="https://en.wikipedia.org/wiki/Linux"><abbr>GNU</abbr>/Linux</a>), 79<a href="https://www.android.com">Android</a>, 80<a href="https://www.freebsd.org">Free<abbr 81title="Berkeley Software Distribution">BSD</abbr></a>, 82<a href="https://netbsd.org">Net<abbr>BSD</abbr></a>, 83<a href="https://www.openbsd.org">Open<abbr>BSD</abbr></a>, | 1<!DOCTYPE html> 2<html lang="en"> 3<head> 4<title>Time zone and daylight saving time data</title> 5<meta charset="UTF-8"> 6<style> 7pre {margin-left: 2em; white-space: pre-wrap;} 8</style> --- 67 unchanged lines hidden (view full) --- 76<abbr title="GNU's Not Unix">GNU</abbr> 77C Library</a> (used in 78<a href="https://en.wikipedia.org/wiki/Linux"><abbr>GNU</abbr>/Linux</a>), 79<a href="https://www.android.com">Android</a>, 80<a href="https://www.freebsd.org">Free<abbr 81title="Berkeley Software Distribution">BSD</abbr></a>, 82<a href="https://netbsd.org">Net<abbr>BSD</abbr></a>, 83<a href="https://www.openbsd.org">Open<abbr>BSD</abbr></a>, |
| 84<a href="https://www.chromium.org/chromium-os/">Chromium OS</a>, | 84<a href="https://www.chromium.org/chromium-os/">ChromiumOS</a>, |
| 85<a href="https://cygwin.com">Cygwin</a>, 86<a href="https://mariadb.org">MariaDB</a>, 87<a href="https://en.wikipedia.org/wiki/MINIX">MINIX</a>, | 85<a href="https://cygwin.com">Cygwin</a>, 86<a href="https://mariadb.org">MariaDB</a>, 87<a href="https://en.wikipedia.org/wiki/MINIX">MINIX</a>, |
| 88<a href="https://musl.libc.org">musl libc</a>, |
|
| 88<a href="https://www.mysql.com">MySQL</a>, 89<a href="https://en.wikipedia.org/wiki/WebOS"><abbr 90title="Web Operating System">webOS</abbr></a>, 91<a href="https://en.wikipedia.org/wiki/IBM_AIX"><abbr 92title="Advanced Interactive eXecutive">AIX</abbr></a>, 93<a href="https://www.apple.com/ios"><abbr 94title="iPhone OS">iOS</abbr></a>, 95<a href="https://www.apple.com/macos">macOS</a>, --- 11 unchanged lines hidden (view full) --- 107represents most of the <abbr title="United States">US</abbr> eastern time zone; 108<code>America/Phoenix</code> represents most of Arizona, which 109uses mountain time without daylight saving time (<abbr>DST</abbr>); 110<code>America/Detroit</code> represents most of Michigan, which uses 111eastern time but with different <abbr>DST</abbr> rules in 1975; 112and other entries represent smaller regions like Starke County, 113Indiana, which switched from central to eastern time in 1991 114and switched back in 2006. | 89<a href="https://www.mysql.com">MySQL</a>, 90<a href="https://en.wikipedia.org/wiki/WebOS"><abbr 91title="Web Operating System">webOS</abbr></a>, 92<a href="https://en.wikipedia.org/wiki/IBM_AIX"><abbr 93title="Advanced Interactive eXecutive">AIX</abbr></a>, 94<a href="https://www.apple.com/ios"><abbr 95title="iPhone OS">iOS</abbr></a>, 96<a href="https://www.apple.com/macos">macOS</a>, --- 11 unchanged lines hidden (view full) --- 108represents most of the <abbr title="United States">US</abbr> eastern time zone; 109<code>America/Phoenix</code> represents most of Arizona, which 110uses mountain time without daylight saving time (<abbr>DST</abbr>); 111<code>America/Detroit</code> represents most of Michigan, which uses 112eastern time but with different <abbr>DST</abbr> rules in 1975; 113and other entries represent smaller regions like Starke County, 114Indiana, which switched from central to eastern time in 1991 115and switched back in 2006. |
| 115To use the database on an extended <a | 116To use the database on a <a |
| 116href="https://en.wikipedia.org/wiki/POSIX"><abbr | 117href="https://en.wikipedia.org/wiki/POSIX"><abbr |
| 117title="Portable Operating System Interface">POSIX</abbr>.1-2017</a> | 118title="Portable Operating System Interface">POSIX</abbr>.1-2024</a> |
| 118implementation set the <code><abbr>TZ</abbr></code> 119environment variable to the location's full name, 120e.g., <code><abbr>TZ</abbr>="America/New_York"</code>.</p> 121<p> 122Associated with each timezone is a history of offsets from 123<a href="https://en.wikipedia.org/wiki/Universal_Time">Universal 124Time</a> (<abbr>UT</abbr>), which is <a 125href="https://en.wikipedia.org/wiki/Greenwich_Mean_Time">Greenwich Mean --- 61 unchanged lines hidden (view full) --- 187Since version 2012e, each release has been tagged in development repositories. 188Untagged commits are less well tested and probably contain 189more errors.</p> 190<p> 191After obtaining the code and data files, see the 192<code>README</code> file for what to do next. 193The code lets you compile the <code><abbr>tz</abbr></code> source files into 194machine-readable binary files, one for each location. The binary files | 119implementation set the <code><abbr>TZ</abbr></code> 120environment variable to the location's full name, 121e.g., <code><abbr>TZ</abbr>="America/New_York"</code>.</p> 122<p> 123Associated with each timezone is a history of offsets from 124<a href="https://en.wikipedia.org/wiki/Universal_Time">Universal 125Time</a> (<abbr>UT</abbr>), which is <a 126href="https://en.wikipedia.org/wiki/Greenwich_Mean_Time">Greenwich Mean --- 61 unchanged lines hidden (view full) --- 188Since version 2012e, each release has been tagged in development repositories. 189Untagged commits are less well tested and probably contain 190more errors.</p> 191<p> 192After obtaining the code and data files, see the 193<code>README</code> file for what to do next. 194The code lets you compile the <code><abbr>tz</abbr></code> source files into 195machine-readable binary files, one for each location. The binary files |
| 195are in a special timezone information format (<dfn><abbr>TZif</abbr></dfn>) 196specified by <a href="https://datatracker.ietf.org/doc/html/8536">Internet 197<abbr>RFC</abbr> 8536</a>. | 196are in a special format specified by 197<a href="https://datatracker.ietf.org/doc/html/8536">The 198Time Zone Information Format (<abbr>TZif</abbr>)</a> 199(Internet <abbr title="Request For Comments">RFC</abbr> 8536). |
| 198The code also lets 199you read a <abbr>TZif</abbr> file and interpret timestamps for that 200location.</p> 201</section> 202 203<section> 204<h2 id="changes">Changes to the <code><abbr>tz</abbr></code> database</h2> 205<p> 206The <code><abbr>tz</abbr></code> code and data 207are by no means authoritative. If you find errors, please | 200The code also lets 201you read a <abbr>TZif</abbr> file and interpret timestamps for that 202location.</p> 203</section> 204 205<section> 206<h2 id="changes">Changes to the <code><abbr>tz</abbr></code> database</h2> 207<p> 208The <code><abbr>tz</abbr></code> code and data 209are by no means authoritative. If you find errors, please |
| 208send changes to <a href="mailto:tz@iana.org"><code>tz@iana.org</code></a>, 209the time zone mailing list. You can also <a 210href="https://mm.icann.org/mailman/listinfo/tz">subscribe</a> to it 211and browse the <a 212href="https://mm.icann.org/pipermail/tz/">archive of old 213messages</a>. 214<a href="https://tzdata-meta.timtimeonline.com/">Metadata for mailing list | 210email changes to <a href="mailto:tz@iana.org"><code>tz@iana.org</code></a>, 211the time zone mailing list. See 212<a href="https://lists.iana.org/postorius/lists/tz.iana.org/">the mailing 213list's main page</a> to subscribe or to browse its archive of old messages. 214<a href="https://tzdata-meta.timtimeonline.com">Metadata for mailing list |
| 215discussions</a> and corresponding data changes can be 216generated <a href="https://github.com/timparenti/tzdata-meta">automatically</a>. 217</p> 218<p> 219Changes to the <code><abbr>tz</abbr></code> code and data are often 220propagated to clients via operating system updates, so 221client <code><abbr>tz</abbr></code> data can often be corrected by 222applying these updates. With GNU/Linux and similar systems, if your 223maintenance provider has not yet adopted the 224latest <code><abbr>tz</abbr></code> data, you can often short-circuit 225the process by tailoring the generic instructions in 226the <code><abbr>tz</abbr> README</code> file and installing the latest 227data yourself. System-specific instructions for installing the 228latest <code><abbr>tz</abbr></code> data have also been published | 215discussions</a> and corresponding data changes can be 216generated <a href="https://github.com/timparenti/tzdata-meta">automatically</a>. 217</p> 218<p> 219Changes to the <code><abbr>tz</abbr></code> code and data are often 220propagated to clients via operating system updates, so 221client <code><abbr>tz</abbr></code> data can often be corrected by 222applying these updates. With GNU/Linux and similar systems, if your 223maintenance provider has not yet adopted the 224latest <code><abbr>tz</abbr></code> data, you can often short-circuit 225the process by tailoring the generic instructions in 226the <code><abbr>tz</abbr> README</code> file and installing the latest 227data yourself. System-specific instructions for installing the 228latest <code><abbr>tz</abbr></code> data have also been published |
| 229for <a href="https://developer.ibm.com/articles/au-aix-olson-time-zone/"><abbr>AIX</abbr></a>, | 229for <a href="https://www.ibm.com/support/pages/aix-time-zone-olson-tzdata-updates"><abbr>AIX</abbr></a>, |
| 230<a 231href="https://source.android.com/devices/tech/config/timezone-rules">Android</a>, 232<a 233href="https://unicode-org.github.io/icu/userguide/datetime/timezone/"><abbr 234title="International Components for Unicode">ICU</abbr></a>, 235<a href="https://www.ibm.com/support/pages/java-sdk-time-zone-update-utility"><abbr>IBM</abbr> 236JDK</a>, 237<a href="https://www.joda.org/joda-time/tz_update.html">Joda-Time</a>, <a --- 5 unchanged lines hidden (view full) --- 243sources for the <code><abbr>tz</abbr></code> database have been 244<a href="https://en.wikipedia.org/wiki/UTF-8"><abbr 245title="Unicode Transformation Format 8-bit">UTF-8</abbr></a> 246<a href="https://en.wikipedia.org/wiki/Text_file">text files</a> 247with lines terminated by <a href="https://en.wikipedia.org/wiki/Newline"><abbr 248title="linefeed">LF</abbr></a>, 249which can be modified by common text editors such 250as <a href="https://www.gnu.org/software/emacs/">GNU Emacs</a>, | 230<a 231href="https://source.android.com/devices/tech/config/timezone-rules">Android</a>, 232<a 233href="https://unicode-org.github.io/icu/userguide/datetime/timezone/"><abbr 234title="International Components for Unicode">ICU</abbr></a>, 235<a href="https://www.ibm.com/support/pages/java-sdk-time-zone-update-utility"><abbr>IBM</abbr> 236JDK</a>, 237<a href="https://www.joda.org/joda-time/tz_update.html">Joda-Time</a>, <a --- 5 unchanged lines hidden (view full) --- 243sources for the <code><abbr>tz</abbr></code> database have been 244<a href="https://en.wikipedia.org/wiki/UTF-8"><abbr 245title="Unicode Transformation Format 8-bit">UTF-8</abbr></a> 246<a href="https://en.wikipedia.org/wiki/Text_file">text files</a> 247with lines terminated by <a href="https://en.wikipedia.org/wiki/Newline"><abbr 248title="linefeed">LF</abbr></a>, 249which can be modified by common text editors such 250as <a href="https://www.gnu.org/software/emacs/">GNU Emacs</a>, |
| 251<a href="https://wiki.gnome.org/Apps/Gedit">gedit</a>, and | 251<a href="https://gedit-technology.github.io/apps/gedit/">gedit</a>, and |
| 252<a href="https://www.vim.org">vim</a>. 253Specialized source-file editing can be done via the 254<a href="https://packagecontrol.io/packages/zoneinfo">Sublime 255zoneinfo</a> package for <a 256href="https://www.sublimetext.com">Sublime Text</a> and the <a 257href="https://marketplace.visualstudio.com/items?itemName=gilmoreorless.vscode-zoneinfo">VSCode 258zoneinfo</a> extension for <a href="https://code.visualstudio.com">Visual 259Studio Code</a>. 260</p> 261<p> 262For further information about updates, please see 263<a href="https://datatracker.ietf.org/doc/html/rfc6557">Procedures for | 252<a href="https://www.vim.org">vim</a>. 253Specialized source-file editing can be done via the 254<a href="https://packagecontrol.io/packages/zoneinfo">Sublime 255zoneinfo</a> package for <a 256href="https://www.sublimetext.com">Sublime Text</a> and the <a 257href="https://marketplace.visualstudio.com/items?itemName=gilmoreorless.vscode-zoneinfo">VSCode 258zoneinfo</a> extension for <a href="https://code.visualstudio.com">Visual 259Studio Code</a>. 260</p> 261<p> 262For further information about updates, please see 263<a href="https://datatracker.ietf.org/doc/html/rfc6557">Procedures for |
| 264Maintaining the Time Zone Database</a> (Internet <abbr 265title="Request For Comments">RFC</abbr> 6557). More detail can be | 264Maintaining the Time Zone Database</a> (Internet <abbr>RFC</abbr> 6557). 265More detail can be |
| 266found in <a href="theory.html">Theory and pragmatics of the 267<code><abbr>tz</abbr></code> code and data</a>. 268<a href="https://a0.github.io/a0-tzmigration/">A0 TimeZone Migration</a> 269displays changes between recent <code><abbr>tzdb</abbr></code> versions. 270</p> 271</section> 272 273<section> --- 121 unchanged lines hidden (view full) --- 395data; see its VTIMEZONE calendar component. 396The iCalendar format requires specialized parsers and generators; a 397variant <a href="https://datatracker.ietf.org/doc/html/rfc6321">xCal</a> 398(Internet <abbr>RFC</abbr> 6321) uses 399<a href="https://www.w3.org/XML/"><abbr 400title="Extensible Markup Language">XML</abbr></a> format, and a variant 401<a href="https://datatracker.ietf.org/doc/html/rfc7265">jCal</a> 402(Internet <abbr>RFC</abbr> 7265) | 266found in <a href="theory.html">Theory and pragmatics of the 267<code><abbr>tz</abbr></code> code and data</a>. 268<a href="https://a0.github.io/a0-tzmigration/">A0 TimeZone Migration</a> 269displays changes between recent <code><abbr>tzdb</abbr></code> versions. 270</p> 271</section> 272 273<section> --- 121 unchanged lines hidden (view full) --- 395data; see its VTIMEZONE calendar component. 396The iCalendar format requires specialized parsers and generators; a 397variant <a href="https://datatracker.ietf.org/doc/html/rfc6321">xCal</a> 398(Internet <abbr>RFC</abbr> 6321) uses 399<a href="https://www.w3.org/XML/"><abbr 400title="Extensible Markup Language">XML</abbr></a> format, and a variant 401<a href="https://datatracker.ietf.org/doc/html/rfc7265">jCal</a> 402(Internet <abbr>RFC</abbr> 7265) |
| 403uses <a href="https://www.json.org"><abbr | 403uses <a href="https://www.json.org/json-en.html"><abbr |
| 404title="JavaScript Object Notation">JSON</abbr></a> format.</li> 405</ul> 406</section> 407 408<section> 409<h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2> 410<p>Although some of these do not fully support 411<code><abbr>tz</abbr></code> data, in recent <code><abbr>tzdb</abbr></code> 412distributions you can generally work around compatibility problems by 413running the command <code>make rearguard_tarballs</code> and compiling 414from the resulting tarballs instead.</p> 415<ul> | 404title="JavaScript Object Notation">JSON</abbr></a> format.</li> 405</ul> 406</section> 407 408<section> 409<h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2> 410<p>Although some of these do not fully support 411<code><abbr>tz</abbr></code> data, in recent <code><abbr>tzdb</abbr></code> 412distributions you can generally work around compatibility problems by 413running the command <code>make rearguard_tarballs</code> and compiling 414from the resulting tarballs instead.</p> 415<ul> |
| 416<li><a href="https://sourceforge.net/projects/vzic/">Vzic</a> is a <a | 416<li><a href="https://github.com/libical/vzic">Vzic</a> is a <a |
| 417href="https://en.wikipedia.org/wiki/C_(programming_language)">C</a> 418program that compiles 419<code><abbr>tz</abbr></code> source into iCalendar-compatible VTIMEZONE files. 420Vzic is freely 421available under the <a 422href="https://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr> 423General Public License (<abbr 424title="General Public License">GPL</abbr>)</a>.</li> --- 10 unchanged lines hidden (view full) --- 435which is freely 436available under both the <abbr>GPL</abbr> and the Perl Artistic 437License. DateTime::TimeZone also contains a script 438<code>tests_from_zdump</code> that generates test cases for each clock 439transition in the <code><abbr>tz</abbr></code> database.</li> 440<li>The <a href="https://howardhinnant.github.io/date/tz.html">Time Zone 441Database Parser</a> is a 442<a href="https://en.wikipedia.org/wiki/C++">C++</a> parser and | 417href="https://en.wikipedia.org/wiki/C_(programming_language)">C</a> 418program that compiles 419<code><abbr>tz</abbr></code> source into iCalendar-compatible VTIMEZONE files. 420Vzic is freely 421available under the <a 422href="https://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr> 423General Public License (<abbr 424title="General Public License">GPL</abbr>)</a>.</li> --- 10 unchanged lines hidden (view full) --- 435which is freely 436available under both the <abbr>GPL</abbr> and the Perl Artistic 437License. DateTime::TimeZone also contains a script 438<code>tests_from_zdump</code> that generates test cases for each clock 439transition in the <code><abbr>tz</abbr></code> database.</li> 440<li>The <a href="https://howardhinnant.github.io/date/tz.html">Time Zone 441Database Parser</a> is a 442<a href="https://en.wikipedia.org/wiki/C++">C++</a> parser and |
| 443runtime library with <a 444href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0355r7.html">API</a> 445adopted by 446<a href="https://en.wikipedia.org/wiki/C++20">C++20</a>, 447the current iteration of the C++ standard. | 443runtime library with a <a 444href="https://en.cppreference.com/w/cpp/chrono"><code>std::chrono</code> API</a> 445that is a standard part of C++. |
| 448It is freely available under the 449<abbr title="Massachusetts Institute of Technology">MIT</abbr> license.</li> 450<li><a id="ICU" href="https://icu.unicode.org">International Components for 451Unicode (<abbr>ICU</abbr>)</a> contains C/C++ and <a 452href="https://en.wikipedia.org/wiki/Java_(programming_language)">Java</a> 453libraries for internationalization that 454has a compiler from <code><abbr>tz</abbr></code> source 455and from <abbr title="Common Locale Data Repository">CLDR</abbr> data --- 6 unchanged lines hidden (view full) --- 462and compiles <code><abbr>tz</abbr></code> source and exposes <abbr 463title="Application Program Interface">API</abbr>s for use. It is 464freely available under the <abbr>MIT</abbr> license.</li> 465<li>Java-based compilers and libraries include: 466<ul> 467<li>The <a 468href="https://www.oracle.com/java/technologies/javase/tzupdater-readme.html">TZUpdater 469tool</a> compiles <code><abbr>tz</abbr></code> source into the format used by | 446It is freely available under the 447<abbr title="Massachusetts Institute of Technology">MIT</abbr> license.</li> 448<li><a id="ICU" href="https://icu.unicode.org">International Components for 449Unicode (<abbr>ICU</abbr>)</a> contains C/C++ and <a 450href="https://en.wikipedia.org/wiki/Java_(programming_language)">Java</a> 451libraries for internationalization that 452has a compiler from <code><abbr>tz</abbr></code> source 453and from <abbr title="Common Locale Data Repository">CLDR</abbr> data --- 6 unchanged lines hidden (view full) --- 460and compiles <code><abbr>tz</abbr></code> source and exposes <abbr 461title="Application Program Interface">API</abbr>s for use. It is 462freely available under the <abbr>MIT</abbr> license.</li> 463<li>Java-based compilers and libraries include: 464<ul> 465<li>The <a 466href="https://www.oracle.com/java/technologies/javase/tzupdater-readme.html">TZUpdater 467tool</a> compiles <code><abbr>tz</abbr></code> source into the format used by |
| 470<a href="https://openjdk.java.net/">OpenJDK</a> and 471<a href="https://jdk.java.net/">Oracle JDK</a>. | 468<a href="https://openjdk.org">OpenJDK</a> and 469<a href="https://jdk.java.net">Oracle JDK</a>. |
| 472Although its source code is proprietary, its executable is available under the 473<a href="https://www.oracle.com/a/tech/docs/tzupdater-lic.html">Java SE 474Timezone Updater License Agreement</a>.</li> 475<li>The <a 476href="https://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html">Java 477SE 8 Date and Time</a> <abbr>API</abbr> can be supplemented by <a 478href="https://www.threeten.org/threeten-extra/">ThreeTen-Extra</a>, 479which is freely available under a <abbr>BSD</abbr>-style license.</li> --- 5 unchanged lines hidden (view full) --- 485they can assume Java 8 or later. It is available under the <a 486href="https://www.apache.org/licenses/LICENSE-2.0">Apache License</a>.</li> 487<li><a href="https://bell-sw.com/pages/iana-updater/">IANA Updater</a> and <a 488href="https://www.azul.com/products/open-source-tools/ziupdater-time-zone-tool/">ZIUpdater</a> 489are alternatives to TZUpdater. IANA Updater's license is unclear; 490ZIUpdater is licensed under the <abbr>GPL</abbr>.</li> 491<li><a href="https://github.com/MenoData/Time4A">Time4A: Advanced date and 492time library for Android</a> and | 470Although its source code is proprietary, its executable is available under the 471<a href="https://www.oracle.com/a/tech/docs/tzupdater-lic.html">Java SE 472Timezone Updater License Agreement</a>.</li> 473<li>The <a 474href="https://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html">Java 475SE 8 Date and Time</a> <abbr>API</abbr> can be supplemented by <a 476href="https://www.threeten.org/threeten-extra/">ThreeTen-Extra</a>, 477which is freely available under a <abbr>BSD</abbr>-style license.</li> --- 5 unchanged lines hidden (view full) --- 483they can assume Java 8 or later. It is available under the <a 484href="https://www.apache.org/licenses/LICENSE-2.0">Apache License</a>.</li> 485<li><a href="https://bell-sw.com/pages/iana-updater/">IANA Updater</a> and <a 486href="https://www.azul.com/products/open-source-tools/ziupdater-time-zone-tool/">ZIUpdater</a> 487are alternatives to TZUpdater. IANA Updater's license is unclear; 488ZIUpdater is licensed under the <abbr>GPL</abbr>.</li> 489<li><a href="https://github.com/MenoData/Time4A">Time4A: Advanced date and 490time library for Android</a> and |
| 493<a href="https://github.com/MenoData/Time4J/">Time4J: Advanced date, | 491<a href="https://github.com/MenoData/Time4J">Time4J: Advanced date, |
| 494time and interval library for Java</a> compile 495<code><abbr>tz</abbr></code> source into a binary format. 496Time4A is available under the Apache License and Time4J is 497available under the <a 498href="https://www.gnu.org/copyleft/lesser.html"><abbr>GNU</abbr> Lesser 499General Public License (<abbr title="Lesser General Public 500License">LGPL</abbr>)</a>.</li> 501<li><abbr>ICU</abbr> (mentioned <a href="#ICU">above</a>) contains compilers and --- 9 unchanged lines hidden (view full) --- 511<code>timeZone</code> option of <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat"><code>Intl.DateTimeFormat</code></a>. 512This can be used as-is or with most of the following libraries, 513many of which also support runtimes lacking the <code>timeZone</code> option. 514<ul> 515<li>The <a 516href="https://github.com/formatjs/date-time-format-timezone"><code>Intl.DateTimeFormat</code> 517timezone polyfill</a> 518is freely available under a <abbr>BSD</abbr>-style license.</li> | 492time and interval library for Java</a> compile 493<code><abbr>tz</abbr></code> source into a binary format. 494Time4A is available under the Apache License and Time4J is 495available under the <a 496href="https://www.gnu.org/copyleft/lesser.html"><abbr>GNU</abbr> Lesser 497General Public License (<abbr title="Lesser General Public 498License">LGPL</abbr>)</a>.</li> 499<li><abbr>ICU</abbr> (mentioned <a href="#ICU">above</a>) contains compilers and --- 9 unchanged lines hidden (view full) --- 509<code>timeZone</code> option of <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat"><code>Intl.DateTimeFormat</code></a>. 510This can be used as-is or with most of the following libraries, 511many of which also support runtimes lacking the <code>timeZone</code> option. 512<ul> 513<li>The <a 514href="https://github.com/formatjs/date-time-format-timezone"><code>Intl.DateTimeFormat</code> 515timezone polyfill</a> 516is freely available under a <abbr>BSD</abbr>-style license.</li> |
| 519<li>The <a href="https://date-fns.org/">date-fns</a> | 517<li>The <a href="https://date-fns.org">date-fns</a> |
| 520library manipulates timezone-aware timestamps in browsers and 521in <a href="https://nodejs.org/en/">Node.js</a>. 522It is freely available under the <abbr>MIT</abbr> license.</li> 523<li><a href="https://github.com/iamkun/dayjs">Day.js</a> is a 524minimalist replacement for the date and time API of 525the <a href="https://momentjs.com/docs/">now-legacy Moment.js</a> date 526manipulation library. 527It is freely available under the <abbr>MIT</abbr> license.</li> --- 19 unchanged lines hidden (view full) --- 547It is freely available under the <abbr>MIT</abbr> license.</li> 548</ul> 549The proposed <a 550href="https://github.com/tc39/proposal-temporal"><code>Temporal</code> 551objects</a> let programs access an abstract view of 552<code><abbr>tzdb</abbr></code> data, and are designed to replace <a 553href="https://codeofmatt.com/javascript-date-type-is-horribly-broken/">JavaScript's 554problematic <code>Date</code> objects</a> when working with dates and times. | 518library manipulates timezone-aware timestamps in browsers and 519in <a href="https://nodejs.org/en/">Node.js</a>. 520It is freely available under the <abbr>MIT</abbr> license.</li> 521<li><a href="https://github.com/iamkun/dayjs">Day.js</a> is a 522minimalist replacement for the date and time API of 523the <a href="https://momentjs.com/docs/">now-legacy Moment.js</a> date 524manipulation library. 525It is freely available under the <abbr>MIT</abbr> license.</li> --- 19 unchanged lines hidden (view full) --- 545It is freely available under the <abbr>MIT</abbr> license.</li> 546</ul> 547The proposed <a 548href="https://github.com/tc39/proposal-temporal"><code>Temporal</code> 549objects</a> let programs access an abstract view of 550<code><abbr>tzdb</abbr></code> data, and are designed to replace <a 551href="https://codeofmatt.com/javascript-date-type-is-horribly-broken/">JavaScript's 552problematic <code>Date</code> objects</a> when working with dates and times. |
| 555<li><a href="https://github.com/JuliaTime/">JuliaTime</a> contains a | 553<li><a href="https://github.com/JuliaTime">JuliaTime</a> contains a |
| 556compiler from <code><abbr>tz</abbr></code> source into | 554compiler from <code><abbr>tz</abbr></code> source into |
| 557<a href="https://julialang.org/">Julia</a>. It is freely available | 555<a href="https://julialang.org">Julia</a>. It is freely available |
| 558under the <abbr>MIT</abbr> license.</li> 559<li><a href="https://github.com/pavkam/tzdb"><abbr>TZDB</abbr> – 560<abbr>IANA</abbr> Time Zone Database for Delphi/<abbr 561title="Free Pascal Compiler">FPC</abbr></a> 562compiles from <code><abbr>tz</abbr></code> source into 563<a href="https://en.wikipedia.org/wiki/Object_Pascal">Object Pascal</a> 564as compiled by <a href="https://en.wikipedia.org/wiki/Delphi_(IDE)">Delphi</a> 565and <a 566href="https://en.wikipedia.org/wiki/Free_Pascal"><abbr>FPC</abbr></a>. 567It is freely available under a <abbr>BSD</abbr>-style license.</li> | 556under the <abbr>MIT</abbr> license.</li> 557<li><a href="https://github.com/pavkam/tzdb"><abbr>TZDB</abbr> – 558<abbr>IANA</abbr> Time Zone Database for Delphi/<abbr 559title="Free Pascal Compiler">FPC</abbr></a> 560compiles from <code><abbr>tz</abbr></code> source into 561<a href="https://en.wikipedia.org/wiki/Object_Pascal">Object Pascal</a> 562as compiled by <a href="https://en.wikipedia.org/wiki/Delphi_(IDE)">Delphi</a> 563and <a 564href="https://en.wikipedia.org/wiki/Free_Pascal"><abbr>FPC</abbr></a>. 565It is freely available under a <abbr>BSD</abbr>-style license.</li> |
| 568<li><a href="http://pytz.sourceforge.net">pytz – World Timezone | 566<li><a href="https://pythonhosted.org/pytz/">pytz – World Timezone |
| 569Definitions for Python</a> compiles <code><abbr>tz</abbr></code> source into 570<a href="https://www.python.org">Python</a>. 571It is freely available under a <abbr>BSD</abbr>-style license. 572In code that can assume Python 3.6 or later it is largely superseded; see <a 573href="https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html">pytz: 574The Fastest Footgun in the West</a>.</li> 575<li><a href="https://tzinfo.github.io">TZInfo – 576Ruby Timezone Library</a> --- 39 unchanged lines hidden (view full) --- 616<li><a href="https://github.com/google/cctz">CCTZ</a> is a simple C++ 617library that translates between <abbr>UT</abbr> and civil time and 618can read <abbr>TZif</abbr> files. It is freely available under the Apache 619License.</li> 620<li>The 621<a href="https://github.com/nayarsystems/posix_tz_db"><code>posix_tz_db</code> 622package</a> contains Python code 623to generate <abbr>CSV</abbr> and <abbr>JSON</abbr> tables that map | 567Definitions for Python</a> compiles <code><abbr>tz</abbr></code> source into 568<a href="https://www.python.org">Python</a>. 569It is freely available under a <abbr>BSD</abbr>-style license. 570In code that can assume Python 3.6 or later it is largely superseded; see <a 571href="https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html">pytz: 572The Fastest Footgun in the West</a>.</li> 573<li><a href="https://tzinfo.github.io">TZInfo – 574Ruby Timezone Library</a> --- 39 unchanged lines hidden (view full) --- 614<li><a href="https://github.com/google/cctz">CCTZ</a> is a simple C++ 615library that translates between <abbr>UT</abbr> and civil time and 616can read <abbr>TZif</abbr> files. It is freely available under the Apache 617License.</li> 618<li>The 619<a href="https://github.com/nayarsystems/posix_tz_db"><code>posix_tz_db</code> 620package</a> contains Python code 621to generate <abbr>CSV</abbr> and <abbr>JSON</abbr> tables that map |
| 624<code><abbr>tz</abbr></code> settings to POSIX.1-2017-like approximations. | 622<code><abbr>tz</abbr></code> settings to proleptic TZ approximations. |
| 625For example, it maps <code>"Africa/Cairo"</code> 626to <code>"EET-2EEST,M4.5.5/0,M10.5.4/24"</code>, 627an approximation valid for Cairo timestamps from 2023 on. | 623For example, it maps <code>"Africa/Cairo"</code> 624to <code>"EET-2EEST,M4.5.5/0,M10.5.4/24"</code>, 625an approximation valid for Cairo timestamps from 2023 on. |
| 628This can help porting to platforms that support only POSIX.1-2017. | 626This can help porting to platforms that support only proleptic TZ. |
| 629The package is freely available under the MIT license.</li> 630<li><a href="https://github.com/derickr/timelib">Timelib</a> is a C 631library that reads <abbr>TZif</abbr> files and converts 632timestamps from one time zone or format to another. 633It is used by <a href="https://secure.php.net"><abbr 634title="PHP: Hypertext Preprocessor">PHP</abbr></a>, 635<a href="https://hhvm.com"><abbr title="HipHop Virtual Machine">HHVM</abbr></a>, 636and <a href="https://www.mongodb.com">MongoDB</a>. --- 7 unchanged lines hidden (view full) --- 644(dual <abbr>GPL</abbr> and Artistic license).</li> 645<li>Python has a <a id="python-zoneinfo" 646href="https://docs.python.org/3/library/zoneinfo.html"><code>zoneinfo.ZoneInfo</code> 647class</a> that reads <abbr>TZif</abbr> data and creates objects 648that represent <code><abbr>tzdb</abbr></code> timezones. 649Python is freely available under the 650<a href="https://docs.python.org/3/license.html">Python Software Foundation 651License</a>. | 627The package is freely available under the MIT license.</li> 628<li><a href="https://github.com/derickr/timelib">Timelib</a> is a C 629library that reads <abbr>TZif</abbr> files and converts 630timestamps from one time zone or format to another. 631It is used by <a href="https://secure.php.net"><abbr 632title="PHP: Hypertext Preprocessor">PHP</abbr></a>, 633<a href="https://hhvm.com"><abbr title="HipHop Virtual Machine">HHVM</abbr></a>, 634and <a href="https://www.mongodb.com">MongoDB</a>. --- 7 unchanged lines hidden (view full) --- 642(dual <abbr>GPL</abbr> and Artistic license).</li> 643<li>Python has a <a id="python-zoneinfo" 644href="https://docs.python.org/3/library/zoneinfo.html"><code>zoneinfo.ZoneInfo</code> 645class</a> that reads <abbr>TZif</abbr> data and creates objects 646that represent <code><abbr>tzdb</abbr></code> timezones. 647Python is freely available under the 648<a href="https://docs.python.org/3/license.html">Python Software Foundation 649License</a>. |
| 652A companion <a id="pypi-tzdata" href="https://pypi.org/">PyPI</a> module | 650A companion <a id="pypi-tzdata" href="https://pypi.org">PyPI</a> module |
| 653<a href="https://pypi.org/project/tzdata/"><code>tzdata</code></a> 654supplies TZif data if the underlying system data cannot be found; 655it is freely available under the Apache License.</li> 656<li>The 657public-domain <a href="https://github.com/dbaron/tz.js">tz.js</a> 658library contains a Python tool that 659converts <abbr>TZif</abbr> data into 660<abbr>JSON</abbr>-format data suitable for use --- 231 unchanged lines hidden (view full) --- 892<dd><a href="https://kalendar.beda.cz/kdy-zacina-a-konci-letni-cas" 893hreflang="cs">When daylight saving time starts and ends (in Czech)</a> 894summarizes and cites historical <abbr>DST</abbr> regulations.</dd> 895<dt>Germany</dt> 896<dd>The National Institute for Science and Technology maintains the <a 897href="https://www.ptb.de/cms/en/fachabteilungen/abt4/fb-44/ag-441/realisation-of-legal-time-in-germany.html">Realisation 898of Legal Time in Germany</a>.</dd> 899<dt>Israel</dt> | 651<a href="https://pypi.org/project/tzdata/"><code>tzdata</code></a> 652supplies TZif data if the underlying system data cannot be found; 653it is freely available under the Apache License.</li> 654<li>The 655public-domain <a href="https://github.com/dbaron/tz.js">tz.js</a> 656library contains a Python tool that 657converts <abbr>TZif</abbr> data into 658<abbr>JSON</abbr>-format data suitable for use --- 231 unchanged lines hidden (view full) --- 890<dd><a href="https://kalendar.beda.cz/kdy-zacina-a-konci-letni-cas" 891hreflang="cs">When daylight saving time starts and ends (in Czech)</a> 892summarizes and cites historical <abbr>DST</abbr> regulations.</dd> 893<dt>Germany</dt> 894<dd>The National Institute for Science and Technology maintains the <a 895href="https://www.ptb.de/cms/en/fachabteilungen/abt4/fb-44/ag-441/realisation-of-legal-time-in-germany.html">Realisation 896of Legal Time in Germany</a>.</dd> 897<dt>Israel</dt> |
| 900<dd>The Interior Ministry periodically issues <a 901href="ftp://ftp.cs.huji.ac.il/pub/tz/announcements" 902hreflang="he">announcements (in Hebrew)</a>.</dd> | 898<dd><a 899href="https://tz.cs.huji.ac.il">Israel Timezone Files</a> 900lists official time-change announcements and laws since 1940, 901almost all in Hebrew.</dd> |
| 903<dt>Malaysia</dt> 904<dd>See Singapore <a href="#Singapore">below</a>.</dd> 905<dt>Mexico</dt> 906<dd>The Investigation and Analysis Service of the Mexican Library of 907Congress has published a <a 908href="https://www.diputados.gob.mx/bibliot/publica/inveyana/polisoc/horver/index.htm" 909hreflang="es">history of Mexican local time (in Spanish)</a>.</dd> 910<dt>Netherlands</dt> --- 165 unchanged lines hidden (view full) --- 1076which corresponds to the first leap second 10771972-06-30 23:59:60 <abbr>UTC</abbr> in the "<code>right</code>" configuration, 1078and to 10791972-07-01 00:00:00 <abbr>UTC</abbr> in the "<code>posix</code>" configuration. 1080In practice the two configurations also agree for timestamps before 10811972 even though the historical situation is messy, partly because 1082neither <abbr>UTC</abbr> nor <abbr>TAI</abbr> 1083is well-defined for sufficiently old timestamps.</li> | 902<dt>Malaysia</dt> 903<dd>See Singapore <a href="#Singapore">below</a>.</dd> 904<dt>Mexico</dt> 905<dd>The Investigation and Analysis Service of the Mexican Library of 906Congress has published a <a 907href="https://www.diputados.gob.mx/bibliot/publica/inveyana/polisoc/horver/index.htm" 908hreflang="es">history of Mexican local time (in Spanish)</a>.</dd> 909<dt>Netherlands</dt> --- 165 unchanged lines hidden (view full) --- 1075which corresponds to the first leap second 10761972-06-30 23:59:60 <abbr>UTC</abbr> in the "<code>right</code>" configuration, 1077and to 10781972-07-01 00:00:00 <abbr>UTC</abbr> in the "<code>posix</code>" configuration. 1079In practice the two configurations also agree for timestamps before 10801972 even though the historical situation is messy, partly because 1081neither <abbr>UTC</abbr> nor <abbr>TAI</abbr> 1082is well-defined for sufficiently old timestamps.</li> |
| 1083<li><a href="https://kb.meinbergglobal.com/kb/time_sync/ntp/configuration/ntp_leap_second_file">The 1084<abbr>NTP</abbr> Leap Second File</a> covers the text file 1085<code>leap-seconds.list</code>, which lists the currently known leap seconds. 1086The <abbr>IERS</abbr> maintains this file, and a copy is distributed by 1087<code><abbr>tzdb</abbr></code> for use by <abbr>NTP</abbr> implementations like 1088<a href="https://www.ntp.org">classic 1089<code><abbr title="Network Time Protocol Daemon">ntpd</abbr></code></a> 1090and <a href="https://ntpsec.org">NTPsec</a>. 1091The <code><abbr>tz</abbr></code> database also distributes leap second 1092information in a differently-formatted <code>leapseconds</code> text file, 1093as well as in the "<code>right</code>" configuration in binary form; for 1094example, <code>right/UTC</code> can be used 1095by <a href="https://chrony-project.org"><code>chrony</code></a>, 1096another <abbr>NTP</abbr> implementation.</li> |
|
| 1084<li><a href="https://developers.google.com/time/smear">Leap Smear</a> 1085discusses how to gradually adjust <abbr>POSIX</abbr> clocks near a 1086leap second so that they disagree with <abbr>UTC</abbr> by at most a 1087half second, even though every <abbr>POSIX</abbr> minute has exactly 1088sixty seconds. This approach works with the default <code><abbr>tz</abbr></code> 1089"<code>posix</code>" configuration, is <a 1090href="http://bk1.ntp.org/ntp-stable/README.leapsmear">supported</a> by | 1097<li><a href="https://developers.google.com/time/smear">Leap Smear</a> 1098discusses how to gradually adjust <abbr>POSIX</abbr> clocks near a 1099leap second so that they disagree with <abbr>UTC</abbr> by at most a 1100half second, even though every <abbr>POSIX</abbr> minute has exactly 1101sixty seconds. This approach works with the default <code><abbr>tz</abbr></code> 1102"<code>posix</code>" configuration, is <a 1103href="http://bk1.ntp.org/ntp-stable/README.leapsmear">supported</a> by |
| 1091the <abbr>NTP</abbr> reference implementation, <a | 1104the abovementioned <abbr>NTP</abbr> implementations, <a |
| 1092href="https://github.com/google/unsmear">supports</a> conversion between 1093<abbr>UTC</abbr> and smeared <abbr>POSIX</abbr> timestamps, and is used by major 1094cloud service providers. However, according to 1095<a href="https://datatracker.ietf.org/doc/html/rfc8633#section-3.7.1">§3.7.1 of 1096Network Time Protocol Best Current Practices</a> 1097(Internet <abbr>RFC</abbr> 8633), leap smearing is not suitable for 1098applications requiring accurate <abbr>UTC</abbr> or civil time, 1099and is intended for use only in single, well-controlled environments.</li> --- 6 unchanged lines hidden (view full) --- 1106<a href="https://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf">The 1107leap second: its history and possible future</a>. 1108<a href="https://www.ucolick.org/~sla/leapsecs/"><abbr>UTC</abbr> 1109might be redefined 1110without Leap Seconds</a> gives pointers on this 1111contentious issue. 1112The General Conference on Weights and Measures 1113<a href="https://www.bipm.org/en/cgpm-2022/resolution-4">decided in 2022</a> | 1105href="https://github.com/google/unsmear">supports</a> conversion between 1106<abbr>UTC</abbr> and smeared <abbr>POSIX</abbr> timestamps, and is used by major 1107cloud service providers. However, according to 1108<a href="https://datatracker.ietf.org/doc/html/rfc8633#section-3.7.1">§3.7.1 of 1109Network Time Protocol Best Current Practices</a> 1110(Internet <abbr>RFC</abbr> 8633), leap smearing is not suitable for 1111applications requiring accurate <abbr>UTC</abbr> or civil time, 1112and is intended for use only in single, well-controlled environments.</li> --- 6 unchanged lines hidden (view full) --- 1119<a href="https://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf">The 1120leap second: its history and possible future</a>. 1121<a href="https://www.ucolick.org/~sla/leapsecs/"><abbr>UTC</abbr> 1122might be redefined 1123without Leap Seconds</a> gives pointers on this 1124contentious issue. 1125The General Conference on Weights and Measures 1126<a href="https://www.bipm.org/en/cgpm-2022/resolution-4">decided in 2022</a> |
| 1114to discontinue the use of leap seconds by 2035, replacing them with an 1115as-yet-undetermined scheme some time after the year 2135. | 1127to discontinue the use of leap seconds by 2035, and requested that no 1128discontinuous adjustments be made to UTC for at least a century. |
| 1116The World Radiocommunication Conference <a 1117href="https://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-WRC.15-2023-PDF-E.pdf">resolved 1118in 2023</a> to cooperate with this process. | 1129The World Radiocommunication Conference <a 1130href="https://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-WRC.15-2023-PDF-E.pdf">resolved 1131in 2023</a> to cooperate with this process. |
| 1132<a href="https://www.preprints.org/manuscript/202406.0043/v1">A proposal 1133to change the leap-second adjustments to Coordinated Universal Time</a> 1134(doi:<a href="https://doi.org/10.1088/1681-7575/ad6266">10.1088/1681-7575/ad6266</a>) 1135would replace leap seconds with 13-second leap smears occurring once per 1136decade until 2100, with leap smears after that gradually increasing in size. 1137However, there is still no consensus on whether this is the best way 1138to replace leap seconds. |
|
| 1119</li> 1120</ul> 1121</section> 1122 1123<section> 1124<h2 id="notation">Time notation</h2> 1125<ul> 1126<li>The <a id="CLDR" href="https://cldr.unicode.org">Unicode Common Locale Data --- 21 unchanged lines hidden (view full) --- 1148<li><a href="https://datatracker.ietf.org/doc/html/rfc5322#section-3.3">§3.3 of 1149Internet Message Format</a> (Internet <abbr>RFC</abbr> 5322) 1150specifies the time notation used in email and <a 1151href="https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol"><abbr>HTTP</abbr></a> 1152headers.</li> 1153<li> 1154<a href="https://datatracker.ietf.org/doc/html/rfc3339">Date and Time 1155on the Internet: Timestamps</a> (Internet <abbr>RFC</abbr> 3339) | 1139</li> 1140</ul> 1141</section> 1142 1143<section> 1144<h2 id="notation">Time notation</h2> 1145<ul> 1146<li>The <a id="CLDR" href="https://cldr.unicode.org">Unicode Common Locale Data --- 21 unchanged lines hidden (view full) --- 1168<li><a href="https://datatracker.ietf.org/doc/html/rfc5322#section-3.3">§3.3 of 1169Internet Message Format</a> (Internet <abbr>RFC</abbr> 5322) 1170specifies the time notation used in email and <a 1171href="https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol"><abbr>HTTP</abbr></a> 1172headers.</li> 1173<li> 1174<a href="https://datatracker.ietf.org/doc/html/rfc3339">Date and Time 1175on the Internet: Timestamps</a> (Internet <abbr>RFC</abbr> 3339) |
| 1156specifies an <abbr>ISO</abbr> 8601 1157profile for use in new Internet 1158protocols.</li> | 1176specifies an <abbr>ISO</abbr> 8601 profile for use in new Internet protocols. 1177An extension, <a href="https://datatracker.ietf.org/doc/html/rfc9557">Date 1178and Time on the Internet: Timestamps with Additional Information</a> 1179(Internet <abbr>RFC</abbr> 9557) extends this profile 1180to let you specify the <code><abbr>tzdb</abbr></code> timezone of a timestamp 1181via suffixes like "<code>[Asia/Tokyo]</code>". |
| 1159<li> 1160<a href="https://web.archive.org/web/20190130042457/https://www.hackcraft.net/web/datetime/">Date & Time 1161Formats on the Web</a> surveys web- and Internet-oriented date and time 1162formats.</li> 1163<li>Alphabetic time zone abbreviations should not be used as unique 1164identifiers for <abbr>UT</abbr> offsets as they are ambiguous in 1165practice. For example, in English-speaking North America 1166"<abbr>CST</abbr>" denotes 6 hours behind <abbr>UT</abbr>, 1167but in China it denotes 8 hours ahead of <abbr>UT</abbr>, 1168and French-speaking North Americans prefer 1169"<abbr title="Heure Normale du Centre">HNC</abbr>" to 1170"<abbr>CST</abbr>". The <code><abbr>tz</abbr></code> 1171database contains English abbreviations for many timestamps; 1172unfortunately some of these abbreviations were merely the database maintainers' 1173inventions, and these have been removed when possible.</li> 1174<li>Numeric time zone abbreviations typically count hours east of 1175<abbr>UT</abbr>, e.g., +09 for Japan and | 1182<li> 1183<a href="https://web.archive.org/web/20190130042457/https://www.hackcraft.net/web/datetime/">Date & Time 1184Formats on the Web</a> surveys web- and Internet-oriented date and time 1185formats.</li> 1186<li>Alphabetic time zone abbreviations should not be used as unique 1187identifiers for <abbr>UT</abbr> offsets as they are ambiguous in 1188practice. For example, in English-speaking North America 1189"<abbr>CST</abbr>" denotes 6 hours behind <abbr>UT</abbr>, 1190but in China it denotes 8 hours ahead of <abbr>UT</abbr>, 1191and French-speaking North Americans prefer 1192"<abbr title="Heure Normale du Centre">HNC</abbr>" to 1193"<abbr>CST</abbr>". The <code><abbr>tz</abbr></code> 1194database contains English abbreviations for many timestamps; 1195unfortunately some of these abbreviations were merely the database maintainers' 1196inventions, and these have been removed when possible.</li> 1197<li>Numeric time zone abbreviations typically count hours east of 1198<abbr>UT</abbr>, e.g., +09 for Japan and |
| 1176−10 for Hawaii. However, the <abbr>POSIX</abbr> 1177<code><abbr>TZ</abbr></code> environment variable uses the opposite convention. | 1199−10 for Hawaii. However, <abbr>POSIX</abbr> proleptic 1200<code><abbr>TZ</abbr></code> settings use the opposite convention. |
| 1178For example, one might use <code><abbr>TZ</abbr>="<abbr 1179title="Japan Standard Time">JST</abbr>-9"</code> and 1180<code><abbr>TZ</abbr>="<abbr title="Hawaii Standard Time">HST</abbr>10"</code> 1181for Japan and Hawaii, respectively. If the 1182<code><abbr>tz</abbr></code> database is available, it is usually better to use 1183settings like <code><abbr>TZ</abbr>="Asia/Tokyo"</code> and 1184<code><abbr>TZ</abbr>="Pacific/Honolulu"</code> instead, as this should avoid 1185confusion, handle old timestamps better, and insulate you better from --- 27 unchanged lines hidden --- | 1201For example, one might use <code><abbr>TZ</abbr>="<abbr 1202title="Japan Standard Time">JST</abbr>-9"</code> and 1203<code><abbr>TZ</abbr>="<abbr title="Hawaii Standard Time">HST</abbr>10"</code> 1204for Japan and Hawaii, respectively. If the 1205<code><abbr>tz</abbr></code> database is available, it is usually better to use 1206settings like <code><abbr>TZ</abbr>="Asia/Tokyo"</code> and 1207<code><abbr>TZ</abbr>="Pacific/Honolulu"</code> instead, as this should avoid 1208confusion, handle old timestamps better, and insulate you better from --- 27 unchanged lines hidden --- |