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3 1.1 christos <head>
4 1.1 christos <title>Sources for time zone and daylight saving time data</title>
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10 1.1 christos <body>
11 1.1 christos <h1>Sources for time zone and daylight saving time data</h1>
12 1.1 christos <p>
13 1.1 christos <a href="https://en.wikipedia.org/wiki/Time_zone">Time zone</a> and
14 1.1 christos <a href="https://en.wikipedia.org/wiki/Daylight_saving_time">daylight-saving</a>
15 1.1 christos rules are controlled by individual
16 1.1 christos governments. They are sometimes changed with little notice, and their
17 1.1 christos histories and planned futures are often recorded only fitfully. Here
18 1.1 christos is a summary of attempts to organize and record relevant data in this
19 1.1 christos area.
20 1.1 christos </p>
21 1.6 christos <h3>Outline</h3>
22 1.6 christos <nav>
23 1.6 christos <ul>
24 1.6 christos <li>The <code><abbr>tz</abbr></code> database product and process
25 1.6 christos <ul>
26 1.6 christos <li><a href="#tzdb">The <code><abbr>tz</abbr></code> database</a></li>
27 1.6 christos <li><a href="#download">Downloading the <code><abbr>tz</abbr></code> database</a></li>
28 1.6 christos <li><a href="#changes">Changes to the <code><abbr>tz</abbr></code> database</a></li>
29 1.6 christos <li><a href="#commentary">Commentary on the <code><abbr>tz</abbr></code> database</a></li>
30 1.6 christos </ul>
31 1.6 christos </li>
32 1.6 christos <li>Uses of the <code><abbr>tz</abbr></code> database
33 1.6 christos <ul>
34 1.6 christos <li><a href="#web">Web sites using recent versions of the <code><abbr>tz</abbr></code> database</a></li>
35 1.6 christos <li><a href="#protocols">Network protocols for <code><abbr>tz</abbr></code> data</a></li>
36 1.6 christos <li><a href="#compilers">Other <code><abbr>tz</abbr></code> compilers</a></li>
37 1.6 christos <li><a href="#TZif">Other <abbr>TZif</abbr> readers</a></li>
38 1.6 christos <li><a href="#software">Other <code><abbr>tz</abbr></code>-based time zone software</a></li>
39 1.6 christos </ul>
40 1.6 christos </li>
41 1.6 christos <li>Related data
42 1.6 christos <ul>
43 1.6 christos <li><a href="#other-dbs">Other time zone databases</a></li>
44 1.6 christos <li><a href="#maps">Maps</a></li>
45 1.6 christos <li><a href="#boundaries">Time zone boundaries</a></li>
46 1.6 christos </ul>
47 1.6 christos </li>
48 1.6 christos <li>Timekeeping concepts
49 1.6 christos <ul>
50 1.6 christos <li><a href="#civil">Civil time concepts and history</a></li>
51 1.6 christos <li><a href="#national">National histories of legal time</a></li>
52 1.6 christos <li><a href="#precision">Precision timekeeping</a></li>
53 1.6 christos <li><a href="#notation">Time notation</a></li>
54 1.6 christos <li><a href="#see-also">See also</a></li>
55 1.6 christos </ul>
56 1.6 christos </li>
57 1.6 christos </ul>
58 1.6 christos </nav>
59 1.6 christos
60 1.6 christos <section>
61 1.1 christos <h2 id="tzdb">The <code><abbr title="time zone">tz</abbr></code> database</h2>
62 1.1 christos <p>
63 1.1 christos The <a href="https://en.wikipedia.org/wiki/Public_domain">public-domain</a>
64 1.1 christos time zone database contains code and data
65 1.1 christos that represent the history of local time
66 1.1 christos for many representative locations around the globe.
67 1.1 christos It is updated periodically to reflect changes made by political bodies
68 1.1 christos to time zone boundaries and daylight saving rules.
69 1.1 christos This database (known as <code><abbr>tz</abbr></code>,
70 1.1 christos <code><abbr>tzdb</abbr></code>, or <code>zoneinfo</code>)
71 1.1 christos is used by several implementations,
72 1.1 christos including
73 1.1 christos <a href="https://www.gnu.org/software/libc/">the
74 1.1 christos <abbr title="GNU's Not Unix">GNU</abbr>
75 1.1 christos C Library</a> (used in
76 1.1 christos <a href="https://en.wikipedia.org/wiki/Linux"><abbr>GNU</abbr>/Linux</a>),
77 1.1 christos <a href="https://www.android.com">Android</a>,
78 1.1 christos <a href="https://www.freebsd.org">Free<abbr
79 1.1 christos title="Berkeley Software Distribution">BSD</abbr></a>,
80 1.1 christos <a href="https://netbsd.org">Net<abbr>BSD</abbr></a>,
81 1.1 christos <a href="https://www.openbsd.org">Open<abbr>BSD</abbr></a>,
82 1.1 christos <a href="https://www.chromium.org/chromium-os">Chromium OS</a>,
83 1.1 christos <a href="https://cygwin.com">Cygwin</a>,
84 1.1 christos <a href="https://en.wikipedia.org/wiki/MINIX">MINIX</a>,
85 1.1 christos <a href="https://www.mysql.com">MySQL</a>,
86 1.1 christos <a href="https://en.wikipedia.org/wiki/WebOS"><abbr
87 1.1 christos title="Web Operating System">webOS</abbr></a>,
88 1.1 christos <a href="https://ibm.com/aix"><abbr
89 1.1 christos title="Advanced Interactive eXecutive">AIX</abbr></a>,
90 1.1 christos <a href="https://en.wikipedia.org/wiki/BlackBerry_10">BlackBerry 10</a>,
91 1.6 christos <a href="https://www.apple.com/ios"><abbr
92 1.1 christos title="iPhone OS">iOS</abbr></a>,
93 1.6 christos <a href="https://www.apple.com/macos">macOS</a>,
94 1.1 christos <a href="https://www.microsoft.com/en-us/windows">Microsoft Windows</a>,
95 1.6 christos <a href="https://www.vmssoftware.com">Open<abbr
96 1.1 christos title="Virtual Memory System">VMS</abbr></a>,
97 1.6 christos <a href="https://www.oracle.com/database/">Oracle Database</a>, and
98 1.1 christos <a href="https://www.oracle.com/solaris">Oracle Solaris</a>.</p>
99 1.1 christos <p>
100 1.2 christos Each main entry in the database represents a <dfn>timezone</dfn>
101 1.2 christos for a set of civil-time clocks that have all agreed since 1970.
102 1.2 christos Timezones are typically identified by continent or ocean and then by the
103 1.2 christos name of the largest city within the region containing the clocks.
104 1.1 christos For example, <code>America/New_York</code>
105 1.1 christos represents most of the <abbr title="United States">US</abbr> eastern time zone;
106 1.1 christos <code>America/Phoenix</code> represents most of Arizona, which
107 1.2 christos uses mountain time without daylight saving time (<abbr>DST</abbr>);
108 1.1 christos <code>America/Detroit</code> represents most of Michigan, which uses
109 1.1 christos eastern time but with different <abbr>DST</abbr> rules in 1975;
110 1.1 christos and other entries represent smaller regions like Starke County,
111 1.1 christos Indiana, which switched from central to eastern time in 1991
112 1.1 christos and switched back in 2006.
113 1.1 christos To use the database on an extended <a
114 1.1 christos href="https://en.wikipedia.org/wiki/POSIX"><abbr
115 1.1 christos title="Portable Operating System Interface">POSIX</abbr></a>
116 1.1 christos implementation set the <code><abbr>TZ</abbr></code>
117 1.1 christos environment variable to the location's full name,
118 1.1 christos e.g., <code><abbr>TZ</abbr>="America/New_York"</code>.</p>
119 1.1 christos <p>
120 1.2 christos Associated with each timezone is a history of offsets from
121 1.1 christos <a href="https://en.wikipedia.org/wiki/Universal_Time">Universal
122 1.1 christos Time</a> (<abbr>UT</abbr>), which is <a
123 1.1 christos href="https://en.wikipedia.org/wiki/Greenwich_Mean_Time">Greenwich Mean
124 1.1 christos Time</a> (<abbr>GMT</abbr>) with days beginning at midnight;
125 1.2 christos for timestamps after 1960 this is more precisely <a
126 1.1 christos href="https://en.wikipedia.org/wiki/Coordinated_Universal_Time">Coordinated
127 1.1 christos Universal Time</a> (<abbr>UTC</abbr>).
128 1.1 christos The database also records when daylight saving time was in use,
129 1.1 christos along with some time zone abbreviations such as <abbr>EST</abbr>
130 1.1 christos for Eastern Standard Time in the <abbr>US</abbr>.</p>
131 1.6 christos </section>
132 1.6 christos
133 1.6 christos <section>
134 1.1 christos <h2 id="download">Downloading the <code><abbr>tz</abbr></code> database</h2>
135 1.1 christos <p>
136 1.1 christos The following <a
137 1.1 christos href="https://en.wikipedia.org/wiki/Unix_shell">shell</a> commands download
138 1.1 christos the latest release's two
139 1.1 christos <a href="https://en.wikipedia.org/wiki/Tar_(computing)">tarballs</a>
140 1.1 christos to a <abbr>GNU</abbr>/Linux or similar host.</p>
141 1.2 christos <pre><code>mkdir tzdb
142 1.1 christos cd tzdb
143 1.1 christos <a href="https://www.gnu.org/software/wget/">wget</a> https://www.iana.org/time-zones/repository/tzcode-latest.tar.gz
144 1.1 christos wget https://www.iana.org/time-zones/repository/tzdata-latest.tar.gz
145 1.1 christos <a href="https://www.gnu.org/software/gzip/">gzip</a> -dc tzcode-latest.tar.gz | <a href="https://www.gnu.org/software/tar/">tar</a> -xf -
146 1.1 christos gzip -dc tzdata-latest.tar.gz | tar -xf -
147 1.1 christos </code></pre>
148 1.1 christos <p>Alternatively, the following shell commands download the same
149 1.1 christos release in a single-tarball format containing extra data
150 1.1 christos useful for regression testing:</p>
151 1.2 christos <pre><code>wget <a href="https://www.iana.org/time-zones/repository/tzdb-latest.tar.lz">https://www.iana.org/time-zones/repository/tzdb-latest.tar.lz</a>
152 1.1 christos <a href="https://www.nongnu.org/lzip/">lzip</a> -dc tzdb-latest.tar.lz | tar -xf -
153 1.1 christos </code></pre>
154 1.1 christos <p>These commands use convenience links to the latest release
155 1.1 christos of the <code><abbr>tz</abbr></code> database hosted by the
156 1.1 christos <a href="https://www.iana.org/time-zones">Time Zone Database website</a>
157 1.1 christos of the <a href="https://www.iana.org">Internet Assigned Numbers
158 1.1 christos Authority (IANA)</a>.
159 1.1 christos Older releases are in files named
160 1.1 christos <code>tzcode<var>V</var>.tar.gz</code>,
161 1.1 christos <code>tzdata<var>V</var>.tar.gz</code>, and
162 1.1 christos <code>tzdb-<var>V</var>.tar.lz</code>,
163 1.1 christos where <code><var>V</var></code> is the version.
164 1.1 christos Since 1996, each version has been a four-digit year followed by
165 1.1 christos lower-case letter (<samp>a</samp> through <samp>z</samp>,
166 1.1 christos then <samp>za</samp> through <samp>zz</samp>, then <samp>zza</samp>
167 1.1 christos through <samp>zzz</samp>, and so on).
168 1.1 christos Since version 2016h, each release has contained a text file named
169 1.1 christos "<samp>version</samp>" whose first (and currently only) line is the version.
170 1.1 christos The releases are also available in an
171 1.1 christos <a href="ftp://ftp.iana.org/tz/releases/"><abbr
172 1.1 christos title="File Transfer Protocol">FTP</abbr> directory</a> via a
173 1.1 christos less-secure protocol.</p>
174 1.1 christos <p>Alternatively, a development repository of code and data can be
175 1.1 christos retrieved from <a href="https://github.com">GitHub</a> via the shell
176 1.1 christos command:</p>
177 1.2 christos <pre><code><a href="https://git-scm.com">git</a> clone <a href="https://github.com/eggert/tz">https://github.com/eggert/tz</a>
178 1.1 christos </code></pre>
179 1.1 christos <p>
180 1.1 christos Since version 2012e, each release has been tagged in development repositories.
181 1.1 christos Untagged commits are less well tested and probably contain
182 1.1 christos more errors.</p>
183 1.1 christos <p>
184 1.1 christos After obtaining the code and data files, see the
185 1.1 christos <code>README</code> file for what to do next.
186 1.1 christos The code lets you compile the <code><abbr>tz</abbr></code> source files into
187 1.2 christos machine-readable binary files, one for each location. The binary files
188 1.5 christos are in a special timezone information format (<dfn><abbr>TZif</abbr></dfn>)
189 1.5 christos specified by <a href="https://tools.ietf.org/html/8536">Internet
190 1.5 christos <abbr>RFC</abbr> 8536</a>.
191 1.2 christos The code also lets
192 1.2 christos you read a <abbr>TZif</abbr> file and interpret timestamps for that
193 1.1 christos location.</p>
194 1.6 christos </section>
195 1.6 christos
196 1.6 christos <section>
197 1.1 christos <h2 id="changes">Changes to the <code><abbr>tz</abbr></code> database</h2>
198 1.1 christos <p>
199 1.1 christos The <code><abbr>tz</abbr></code> code and data
200 1.1 christos are by no means authoritative. If you find errors, please
201 1.1 christos send changes to <a href="mailto:tz (a] iana.org"><code>tz (a] iana.org</code></a>,
202 1.1 christos the time zone mailing list. You can also <a
203 1.1 christos href="https://mm.icann.org/mailman/listinfo/tz">subscribe</a> to it
204 1.1 christos and browse the <a
205 1.1 christos href="https://mm.icann.org/pipermail/tz/">archive of old
206 1.5 christos messages</a>.
207 1.5 christos <a href="https://tzdata-meta.timtimeonline.com/">Metadata for mailing list
208 1.5 christos discussions</a> and corresponding data changes can be
209 1.5 christos generated <a href="https://github.com/timparenti/tzdata-meta">automatically</a>.
210 1.5 christos </p>
211 1.1 christos <p>
212 1.1 christos If your government plans to change its time zone boundaries or
213 1.1 christos daylight saving rules, inform <code>tz (a] iana.org</code> well in
214 1.1 christos advance, as this will coordinate updates to many cell phones,
215 1.1 christos computers, and other devices around the world. With
216 1.1 christos less than a year's notice there is a good chance that some
217 1.1 christos computer-based clocks will operate incorrectly after the change, due
218 1.1 christos to delays in propagating updates to software and data. The shorter
219 1.1 christos the notice, the more likely clock problems will arise; see "<a
220 1.1 christos href="https://codeofmatt.com/2016/04/23/on-the-timing-of-time-zone-changes/">On
221 1.1 christos the Timing of Time Zone Changes</a>" for examples.
222 1.1 christos </p>
223 1.1 christos <p>
224 1.1 christos Changes to the <code><abbr>tz</abbr></code> code and data are often
225 1.1 christos propagated to clients via operating system updates, so
226 1.1 christos client <code><abbr>tz</abbr></code> data can often be corrected by
227 1.1 christos applying these updates. With GNU/Linux and similar systems, if your
228 1.1 christos maintenance provider has not yet adopted the
229 1.1 christos latest <code><abbr>tz</abbr></code> data, you can often short-circuit
230 1.1 christos the process by tailoring the generic instructions in
231 1.1 christos the <code><abbr>tz</abbr> README</code> file and installing the latest
232 1.1 christos data yourself. System-specific instructions for installing the
233 1.1 christos latest <code><abbr>tz</abbr></code> data have also been published
234 1.1 christos for <a href="https://www.ibm.com/developerworks/aix/library/au-aix-olson-time-zone/index.html"><abbr>AIX</abbr></a>,
235 1.1 christos <a
236 1.1 christos href="https://play.google.com/store/apps/details?id=com.google.android.timezone.data">Android</a>,
237 1.1 christos <a
238 1.1 christos href="http://userguide.icu-project.org/datetime/timezone"><abbr
239 1.1 christos title="International Components for Unicode">ICU</abbr></a>,
240 1.1 christos <a href="https://developer.ibm.com/javasdk/support/dst/jtzu/"><abbr>IBM</abbr></a>
241 1.1 christos and <a
242 1.4 christos href="https://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">Oracle</a>
243 1.4 christos Java, <a href="https://www.joda.org/joda-time/tz_update.html">Joda-Time</a>, <a
244 1.1 christos href="https://dev.mysql.com/doc/refman/en/time-zone-support.html">MySQL</a>,
245 1.1 christos and <a
246 1.1 christos href="https://nodatime.org/userguide/tzdb">Noda Time</a> (see below).
247 1.1 christos </p>
248 1.1 christos <p>Sources for the <code><abbr>tz</abbr></code> database are
249 1.1 christos <a href="https://en.wikipedia.org/wiki/UTF-8"><abbr
250 1.1 christos title="Unicode Transformation Format 8-bit">UTF-8</abbr></a>
251 1.1 christos <a href="https://en.wikipedia.org/wiki/Text_file">text files</a>
252 1.1 christos with lines terminated by <a href="https://en.wikipedia.org/wiki/Newline"><abbr
253 1.1 christos title="linefeed">LF</abbr></a>,
254 1.1 christos which can be modified by common text editors such
255 1.1 christos as <a href="https://www.gnu.org/software/emacs/">GNU Emacs</a>,
256 1.1 christos <a href="https://wiki.gnome.org/Apps/Gedit">gedit</a>, and
257 1.1 christos <a href="https://www.vim.org">vim</a>.
258 1.1 christos Specialized source-file editing can be done via the
259 1.1 christos <a href="https://packagecontrol.io/packages/zoneinfo">Sublime
260 1.1 christos zoneinfo</a> package for <a
261 1.1 christos href="https://www.sublimetext.com">Sublime Text</a> and the <a
262 1.1 christos href="https://marketplace.visualstudio.com/items?itemName=gilmoreorless.vscode-zoneinfo">VSCode
263 1.1 christos zoneinfo</a> extension for <a href="https://code.visualstudio.com">Visual
264 1.1 christos Studio Code</a>.
265 1.1 christos </p>
266 1.1 christos <p>
267 1.1 christos For further information about updates, please see
268 1.1 christos <a href="https://tools.ietf.org/html/rfc6557">Procedures for
269 1.1 christos Maintaining the Time Zone Database</a> (Internet <abbr
270 1.1 christos title="Request For Comments">RFC</abbr> 6557). More detail can be
271 1.1 christos found in <a href="theory.html">Theory and pragmatics of the tz code and data</a>.
272 1.2 christos <a href="https://a0.github.io/a0-tzmigration/">A0 TimeZone Migration</a>
273 1.2 christos displays changes between recent <code><abbr>tzdb</abbr></code> versions.
274 1.1 christos </p>
275 1.6 christos </section>
276 1.6 christos
277 1.6 christos <section>
278 1.1 christos <h2 id="commentary">Commentary on the <code><abbr>tz</abbr></code> database</h2>
279 1.1 christos <ul>
280 1.1 christos <li>The article
281 1.1 christos <a href="https://en.wikipedia.org/wiki/Tz_database">tz database</a> is
282 1.1 christos an encyclopedic summary.</li>
283 1.1 christos <li><a href="tz-how-to.html">How to Read the
284 1.1 christos tz Database Source Files</a> explains the <code><abbr>tz</abbr></code>
285 1.1 christos database format.</li>
286 1.1 christos <li><a
287 1.1 christos href="https://blog.jonudell.net/2009/10/23/a-literary-appreciation-of-the-olsonzoneinfotz-database/">A
288 1.1 christos literary appreciation of the Olson/Zoneinfo/tz database</a> comments on the
289 1.1 christos database's style.</li>
290 1.1 christos </ul>
291 1.6 christos </section>
292 1.6 christos
293 1.6 christos <section>
294 1.1 christos <h2 id="web">Web sites using recent versions of the
295 1.1 christos <code><abbr>tz</abbr></code> database</h2>
296 1.1 christos <p>
297 1.1 christos These are listed roughly in ascending order of complexity and fanciness.
298 1.1 christos </p>
299 1.1 christos <ul>
300 1.1 christos <li><a href="https://time.is">Time.is</a> shows locations'
301 1.1 christos time and zones.</li>
302 1.1 christos <li><a href="https://www.timejones.com">TimeJones.com</a>,
303 1.1 christos <a href="https://timezoneconverterapp.com">Time Zone Converter</a> and
304 1.6 christos <a href="https://worldclock.com">The World Clock</a>
305 1.1 christos are time zone converters.</li>
306 1.1 christos <li><a
307 1.6 christos href="https://twiki.org/cgi-bin/xtra/tzdatepick.html">Date and Time Gateway</a>
308 1.1 christos lets you see the <code><abbr>TZ</abbr></code> values directly.</li>
309 1.1 christos <li><a
310 1.1 christos href="http://www.convertit.com/Go/ConvertIt/World_Time/Current_Time.ASP">Current
311 1.1 christos Time in 1000 Places</a> uses descriptions of the values.</li>
312 1.6 christos <li><a href="https://timezoneconverterapp.com/">Time Zone Converter</a>
313 1.1 christos uses a pulldown menu.</li>
314 1.1 christos <li><a href="http://home.kpn.nl/vanadovv/time/TZworld.html">Complete
315 1.1 christos timezone information for all countries</a> displays tables of DST rules.
316 1.1 christos <li><a href="https://www.timeanddate.com/worldclock/">The World Clock –
317 1.1 christos Worldwide</a> lets you sort zone names and convert times.</li>
318 1.1 christos <li><a href="https://24timezones.com">24TimeZones</a> has a world
319 1.1 christos time map and a time converter.</li>
320 1.1 christos <li><a href="https://www.zeitverschiebung.net/en/">Time Difference</a>
321 1.1 christos calculates the current time difference between locations.</li>
322 1.1 christos <li><a href="http://www.wx-now.com">Weather Now</a> and
323 1.1 christos <a href="http://www.thetimenow.com">The Time Now</a> list the weather too.</li>
324 1.1 christos </ul>
325 1.6 christos </section>
326 1.6 christos
327 1.6 christos <section>
328 1.1 christos <h2 id="protocols">Network protocols for <code><abbr>tz</abbr></code> data</h2>
329 1.1 christos <ul>
330 1.1 christos <li>The <a href="https://www.ietf.org">Internet Engineering Task Force</a>'s
331 1.1 christos <a href="https://datatracker.ietf.org/wg/tzdist/charter/">Time Zone Data
332 1.1 christos Distribution Service (tzdist) working group</a> defined <a
333 1.1 christos href="https://tools.ietf.org/html/rfc7808">TZDIST</a>
334 1.1 christos (Internet <abbr>RFC</abbr> 7808), a time zone data distribution service,
335 1.1 christos along with <a href="https://tools.ietf.org/html/rfc7809">CalDAV</a>
336 1.1 christos (Internet <abbr>RFC</abbr> 7809), a calendar access protocol for
337 1.2 christos transferring time zone data by reference.
338 1.2 christos The <a href="https://www.ietf.org/mailman/listinfo/tzdist-bis">tzdist-bis
339 1.6 christos mailing list</a> discussed the Internet draft <a
340 1.1 christos id="TZDIST-Geolocate"
341 1.2 christos href="https://tools.ietf.org/html/draft-murchison-tzdist-geolocate">TZDIST
342 1.6 christos Geolocate Extension</a> (now expired), which let a client determine its timezone
343 1.1 christos from its geographic location using a <a
344 1.5 christos href="https://tools.ietf.org/html/rfc5870">'geo' URI</a>.</li>
345 1.1 christos <li>The <a href="https://tools.ietf.org/html/rfc5545">
346 1.1 christos Internet Calendaring and Scheduling Core Object Specification
347 1.1 christos (iCalendar)</a> (Internet <abbr>RFC</abbr> 5445)
348 1.1 christos covers time zone
349 1.1 christos data; see its VTIMEZONE calendar component.
350 1.1 christos The iCalendar format requires specialized parsers and generators; a
351 1.1 christos variant <a href="https://tools.ietf.org/html/rfc6321">xCal</a>
352 1.1 christos (Internet <abbr>RFC</abbr> 6321) uses
353 1.1 christos <a href="https://www.w3.org/XML/"><abbr
354 1.1 christos title="Extensible Markup Language">XML</abbr></a> format, and a variant
355 1.1 christos <a href="https://tools.ietf.org/html/rfc7265">jCal</a>
356 1.1 christos (Internet <abbr>RFC</abbr> 7265)
357 1.1 christos uses <a href="https://www.json.org"><abbr
358 1.1 christos title="JavaScript Object Notation">JSON</abbr></a> format.</li>
359 1.1 christos </ul>
360 1.6 christos </section>
361 1.6 christos
362 1.6 christos <section>
363 1.1 christos <h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2>
364 1.1 christos <ul>
365 1.1 christos <li><a href="https://sourceforge.net/projects/vzic/">Vzic</a> is a <a
366 1.1 christos href="https://en.wikipedia.org/wiki/C_%28programming_language%29">C</a>
367 1.1 christos program that compiles
368 1.1 christos <code><abbr>tz</abbr></code> source into iCalendar-compatible VTIMEZONE files.
369 1.1 christos Vzic is freely
370 1.1 christos available under the <a
371 1.1 christos href="https://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr>
372 1.1 christos General Public License (<abbr
373 1.1 christos title="General Public License">GPL</abbr>)</a>.</li>
374 1.1 christos <li><a href="https://sourceforge.net/projects/tzical/">tziCal – tz
375 1.1 christos database conversion utility</a> is like Vzic, except for the <a
376 1.6 christos href="https://dotnet.microsoft.com">.NET framework</a>
377 1.1 christos and with a <abbr>BSD</abbr>-style license.</li>
378 1.1 christos <li><a
379 1.4 christos href="https://metacpan.org/release/DateTime-TimeZone">DateTime::TimeZone</a>
380 1.1 christos contains a script <code>parse_olson</code> that compiles
381 1.1 christos <code><abbr>tz</abbr></code> source into <a href="https://www.perl.org">Perl</a>
382 1.1 christos modules. It is part of the Perl <a
383 1.4 christos href="https://github.com/houseabsolute/DateTime.pm/wiki">DateTime Project</a>,
384 1.4 christos which is freely
385 1.1 christos available under both the <abbr>GPL</abbr> and the Perl Artistic
386 1.1 christos License. DateTime::TimeZone also contains a script
387 1.1 christos <code>tests_from_zdump</code> that generates test cases for each clock
388 1.1 christos transition in the <code><abbr>tz</abbr></code> database.</li>
389 1.1 christos <li>The <a href="https://howardhinnant.github.io/date/tz.html">Time Zone
390 1.1 christos Database Parser</a> is a
391 1.1 christos <a href="https://en.wikipedia.org/wiki/C%2B%2B">C++</a> parser and
392 1.1 christos runtime library that is <a
393 1.1 christos href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0355r4.html">moving
394 1.6 christos forward</a> for inclusion in
395 1.6 christos <a href="https://en.wikipedia.org/wiki/C++20">C++20</a>,
396 1.6 christos the next iteration of the C++ standard.
397 1.1 christos It is freely available under the
398 1.1 christos <abbr title="Massachusetts Institute of Technology">MIT</abbr> license.</li>
399 1.1 christos <li><a id="ICU" href="http://site.icu-project.org">International Components for
400 1.1 christos Unicode (<abbr>ICU</abbr>)</a> contains C/C++ and <a
401 1.1 christos href="https://en.wikipedia.org/wiki/Java_%28programming_language%29">Java</a>
402 1.1 christos libraries for internationalization that
403 1.1 christos has a compiler from <code><abbr>tz</abbr></code> source
404 1.1 christos and from <abbr title="Common Locale Data Repository">CLDR</abbr> data
405 1.1 christos (mentioned <a href="#CLDR">below</a>)
406 1.1 christos into an <abbr>ICU</abbr>-specific format.
407 1.1 christos <abbr>ICU</abbr> is freely available under a
408 1.1 christos <abbr>BSD</abbr>-style license.</li>
409 1.1 christos <li>The <a href="https://github.com/lau/tzdata">Tzdata</a> package for
410 1.1 christos the <a href="https://elixir-lang.org">Elixir</a> language downloads
411 1.1 christos and compiles tz source and exposes <abbr
412 1.1 christos title="Application Program Interface">API</abbr>s for use. It is
413 1.1 christos freely available under the <abbr>MIT</abbr> license.</li>
414 1.1 christos <li>Java-based compilers and libraries include:
415 1.1 christos <ul>
416 1.1 christos <li>The <a
417 1.4 christos href="https://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">TZUpdater
418 1.1 christos tool</a> compiles <code><abbr>tz</abbr></code> source into the format used by
419 1.1 christos Oracle Java.</li>
420 1.1 christos <li>The <a
421 1.4 christos href="https://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html">Java
422 1.6 christos SE 8 Date and Time</a> <abbr>API</abbr> can be supplemented by <a
423 1.4 christos href="https://www.threeten.org/threeten-extra/">ThreeTen-Extra</a>,
424 1.1 christos which is freely available under a <abbr>BSD</abbr>-style license.</li>
425 1.4 christos <li><a href="https://www.joda.org/joda-time/">Joda-Time – Java date
426 1.1 christos and time <abbr>API</abbr></a> contains a class
427 1.1 christos <code>org.joda.time.tz.ZoneInfoCompiler</code> that compiles
428 1.1 christos <code><abbr>tz</abbr></code> source into a binary format. It inspired
429 1.1 christos Java 8 <code>java.time</code>, which its users should migrate to once
430 1.1 christos they can assume Java 8 or later. It is available under the <a
431 1.1 christos href="https://www.apache.org/licenses/LICENSE-2.0">Apache License</a>.</li>
432 1.4 christos <li><a href="https://github.com/MenoData/Time4A">Time4A: Advanced date and
433 1.4 christos time library for Android</a> and
434 1.4 christos <a href="https://github.com/MenoData/Time4J/">Time4J: Advanced date,
435 1.4 christos time and interval library for Java</a> compile
436 1.4 christos <code><abbr>tz</abbr></code> source into a binary format.
437 1.4 christos Time4A is available under the Apache License and Time4J is
438 1.1 christos available under the <a
439 1.1 christos href="https://www.gnu.org/copyleft/lesser.html"><abbr>GNU</abbr> Lesser
440 1.1 christos General Public License (<abbr title="Lesser General Public
441 1.1 christos License">LGPL</abbr>)</a>.</li>
442 1.1 christos <li><abbr>ICU</abbr> (mentioned <a href="#ICU">above</a>) contains compilers and
443 1.1 christos Java-based libraries.</li>
444 1.1 christos </ul>
445 1.1 christos <li><a href="https://nodatime.org">Noda Time – Date and
446 1.1 christos time <abbr>API</abbr> for .NET</a>
447 1.4 christos is like Joda-Time and Time4J, but for the .NET framework instead of Java.
448 1.4 christos It is freely available under the Apache License.</li>
449 1.1 christos <li><a href="https://en.wikipedia.org/wiki/JavaScript">JavaScript</a>-based
450 1.1 christos compilers and libraries include:
451 1.1 christos <ul>
452 1.1 christos <li><a
453 1.1 christos href="https://github.com/kshetline/compact-time-zone-generator">CompactTimeZoneGenerator</a>
454 1.1 christos compiles time zone data into a compact form designed for
455 1.1 christos JavaScript. It is freely available under a combination of
456 1.1 christos the <abbr>MIT</abbr> license and the Apache License.</li>
457 1.1 christos <li><a href="https://momentjs.com/timezone/">Moment Timezone</a> is a
458 1.1 christos plugin for the <a href="https://momentjs.com">Moment.js</a> date
459 1.1 christos manipulation library. It is freely available under the <abbr>MIT</abbr>
460 1.1 christos license.</li>
461 1.1 christos <li><a href="https://github.com/mde/timezone-js">TimezoneJS.Date</a>'s
462 1.1 christos <abbr>API</abbr> is upward compatible with standard JavaScript
463 1.1 christos Dates. It is freely available under the Apache License.</li>
464 1.1 christos </ul>
465 1.1 christos <li><a href="https://github.com/JuliaTime/">JuliaTime</a> contains a
466 1.1 christos compiler from <code><abbr>tz</abbr></code> source into
467 1.1 christos <a href="https://julialang.org/">Julia</a>. It is freely available
468 1.1 christos under the <abbr>MIT</abbr> license.</li>
469 1.6 christos <li><a href="https://github.com/pavkam/tzdb"><abbr>TZDB</abbr> –
470 1.6 christos <abbr>IANA</abbr> Time Zone Database for Delphi/<abbr
471 1.6 christos title="Free Pascal Compiler">FPC</abbr></a>
472 1.2 christos compiles from <code><abbr>tz</abbr></code> source into
473 1.2 christos <a href="https://en.wikipedia.org/wiki/Object_Pascal">Object Pascal</a>
474 1.2 christos as compiled by <a href="https://en.wikipedia.org/wiki/Delphi_(IDE)">Delphi</a>
475 1.2 christos and <a
476 1.2 christos href="https://en.wikipedia.org/wiki/Free_Pascal"><abbr>FPC</abbr></a>.
477 1.2 christos It is freely available under a <abbr>BSD</abbr>-style license.</li>
478 1.1 christos <li><a href="http://pytz.sourceforge.net">pytz – World Timezone
479 1.1 christos Definitions for Python</a> compiles <code><abbr>tz</abbr></code> source into
480 1.1 christos <a href="https://www.python.org">Python</a>.
481 1.1 christos It is freely available under a <abbr>BSD</abbr>-style license.</li>
482 1.1 christos <li><a href="https://tzinfo.github.io">TZInfo –
483 1.1 christos Ruby Timezone Library</a>
484 1.1 christos compiles <code><abbr>tz</abbr></code> source into
485 1.1 christos <a href="https://www.ruby-lang.org/en/">Ruby</a>.
486 1.1 christos It is freely available under the <abbr>MIT</abbr> license.</li>
487 1.1 christos <li>The <a href="http://www.squeaksource.com/Chronos/">Chronos Date/Time
488 1.1 christos Library</a> is
489 1.1 christos a <a href="https://en.wikipedia.org/wiki/Smalltalk">Smalltalk</a> class
490 1.1 christos library that compiles <code><abbr>tz</abbr></code> source into a time
491 1.1 christos zone repository whose format
492 1.1 christos is either proprietary or an <abbr>XML</abbr>-encoded
493 1.1 christos representation.</li>
494 1.1 christos <li><a id="Tcl" href="https://tcl.tk">Tcl</a>
495 1.1 christos contains a developer-oriented parser that compiles <code><abbr>tz</abbr></code>
496 1.1 christos source into text files, along with a runtime that can read those
497 1.1 christos files. Tcl is freely available under a <abbr>BSD</abbr>-style
498 1.1 christos license.</li>
499 1.1 christos </ul>
500 1.6 christos </section>
501 1.6 christos
502 1.6 christos <section>
503 1.2 christos <h2 id="TZif">Other <abbr>TZif</abbr> readers</h2>
504 1.1 christos <ul>
505 1.1 christos <li>The <a
506 1.1 christos href="https://www.gnu.org/software/libc/"><abbr>GNU</abbr> C
507 1.1 christos Library</a>
508 1.1 christos has an independent, thread-safe implementation of
509 1.2 christos a <abbr>TZif</abbr> file reader.
510 1.1 christos This library is freely available under the LGPL
511 1.1 christos and is widely used in <abbr>GNU</abbr>/Linux systems.</li>
512 1.1 christos <li><a href="https://www.gnome.org">GNOME</a>'s
513 1.1 christos <a href="https://developer.gnome.org/glib/">GLib</a> has
514 1.2 christos a <abbr>TZif</abbr> file reader written in C that
515 1.1 christos creates a <code>GTimeZone</code> object representing sets
516 1.1 christos of <abbr>UT</abbr> offsets.
517 1.1 christos It is freely available under the <abbr>LGPL</abbr>.</li>
518 1.1 christos <li>The
519 1.1 christos <a href="https://github.com/bloomberg/bde/wiki">BDE Standard Library</a>'s
520 1.1 christos <code>baltzo::TimeZoneUtil</code> component contains a C++
521 1.2 christos implementation of a <abbr>TZif</abbr> file reader. It is freely available under
522 1.1 christos the Apache License.</li>
523 1.1 christos <li><a href="https://github.com/google/cctz">CCTZ</a> is a simple C++
524 1.1 christos library that translates between <abbr>UT</abbr> and civil time and
525 1.2 christos can read <abbr>TZif</abbr> files. It is freely available under the Apache
526 1.1 christos License.</li>
527 1.1 christos <li><a href="http://bmsi.com/java/#TZ">ZoneInfo.java</a>
528 1.2 christos is a <abbr>TZif</abbr> file reader written in Java.
529 1.1 christos It is freely available under the <abbr>LGPL</abbr>.</li>
530 1.1 christos <li><a href="https://github.com/derickr/timelib">Timelib</a> is a C
531 1.2 christos library that reads <abbr>TZif</abbr> files and converts
532 1.2 christos timestamps from one time zone or format to another.
533 1.1 christos It is used by <a href="https://secure.php.net"><abbr
534 1.1 christos title="PHP: Hypertext Preprocessor">PHP</abbr></a>,
535 1.1 christos <a href="https://hhvm.com"><abbr title="HipHop Virtual Machine">HHVM</abbr></a>,
536 1.1 christos and <a href="https://www.mongodb.com">MongoDB</a>.
537 1.1 christos It is freely available under the <abbr>MIT</abbr> license.</li>
538 1.1 christos <li><a href="https://github.com/bigeasy/timezone">Timezone</a> is a
539 1.1 christos JavaScript library that supports date arithmetic that is time zone
540 1.1 christos aware. It is freely available under the <abbr>MIT</abbr> license.</li>
541 1.1 christos <li>Tcl, mentioned <a href="#Tcl">above</a>, also contains a
542 1.2 christos <abbr>TZif</abbr> file reader.</li>
543 1.4 christos <li><a href="https://metacpan.org/pod/DateTime::TimeZone::Tzfile">
544 1.1 christos DateTime::TimeZone::Tzfile</a>
545 1.2 christos is a <abbr>TZif</abbr> file reader written in Perl.
546 1.1 christos It is freely available under the same terms as Perl
547 1.1 christos (dual <abbr>GPL</abbr> and Artistic license).</li>
548 1.1 christos <li>The
549 1.1 christos public-domain <a href="https://github.com/dbaron/tz.js">tz.js</a>
550 1.1 christos library contains a Python tool that
551 1.2 christos converts <abbr>TZif</abbr> data into
552 1.1 christos <abbr>JSON</abbr>-format data suitable for use
553 1.1 christos in its JavaScript library for time zone conversion. Dates before 1970
554 1.1 christos are not supported.</li>
555 1.1 christos <li>The <a
556 1.1 christos href="https://hackage.haskell.org/package/timezone-olson">timezone-olson</a>
557 1.1 christos package contains <a href="https://www.haskell.org">Haskell</a> code that
558 1.2 christos parses and uses <abbr>TZif</abbr> data. It is freely
559 1.1 christos available under a <abbr>BSD</abbr>-style license.</li>
560 1.1 christos </ul>
561 1.6 christos </section>
562 1.6 christos
563 1.6 christos <section>
564 1.1 christos <h2 id="software">Other <code><abbr>tz</abbr></code>-based time zone software</h2>
565 1.1 christos <ul>
566 1.1 christos <li><a href="https://foxclocks.org">FoxClocks</a>
567 1.1 christos is an extension for <a href="https://www.google.com/chrome/">Google
568 1.1 christos Chrome</a> and for <a
569 1.1 christos href="https://developer.mozilla.org/en-US/docs/Mozilla/Tech/Toolkit_API">Mozilla
570 1.1 christos Toolkit</a> applications like <a
571 1.1 christos href="https://www.mozilla.org/en-US/firefox/new/">Firefox</a> and <a
572 1.1 christos href="https://www.mozilla.org/en-US/thunderbird/">Thunderbird</a>.
573 1.1 christos It displays multiple clocks in the application window, and has a mapping
574 1.1 christos interface to <a href="https://www.google.com/earth/">Google Earth</a>.
575 1.1 christos It is freely available under the <abbr>GPL</abbr>.</li>
576 1.1 christos <li><a href="https://golang.org">Go programming language</a>
577 1.1 christos implementations contain a copy of a 32-bit subset of a recent
578 1.1 christos <code><abbr>tz</abbr></code> database in a
579 1.1 christos Go-specific format.</li>
580 1.1 christos <li><a
581 1.1 christos href="http://users.skynet.be/Peter.Verthez/projects/intclock/">International
582 1.1 christos clock (intclock)</a> is a clock that displays multiple time zones on
583 1.1 christos <abbr>GNU</abbr>/Linux and similar systems. It is freely available
584 1.1 christos under the <abbr>GPL</abbr>.</li>
585 1.1 christos <li>Microsoft Windows 8.1
586 1.1 christos and later has <code><abbr>tz</abbr></code> data and <abbr>CLDR</abbr>
587 1.3 christos data (mentioned <a href="#CLDR">below</a>) used by the
588 1.3 christos <a href="https://en.wikipedia.org/wiki/Windows_Runtime">Windows Runtime</a> /
589 1.3 christos <a href="https://en.wikipedia.org/wiki/Universal_Windows_Platform">Universal Windows Platform</a> classes
590 1.3 christos <a href="https://docs.microsoft.com/uwp/api/Windows.Globalization.DateTimeFormatting.DateTimeFormatter"><code>DateTimeFormatter</code></a> and
591 1.3 christos <a href="https://docs.microsoft.com/uwp/api/windows.globalization.calendar"><code>Calendar</code></a>.
592 1.1 christos <a id="System.TimeZoneInfo"
593 1.1 christos href="https://blogs.msdn.microsoft.com/bclteam/2007/06/07/exploring-windows-time-zones-with-system-timezoneinfo-josh-free/">Exploring
594 1.1 christos Windows Time Zones with <code>System.TimeZoneInfo</code></a> describes
595 1.1 christos the older, proprietary method of Microsoft Windows 2000 and later,
596 1.1 christos which stores time zone data in the
597 1.1 christos <a href="https://en.wikipedia.org/wiki/Windows_Registry">Windows Registry</a>. The
598 1.1 christos <a
599 1.1 christos href="https://unicode.org/cldr/charts/latest/supplemental/zone_tzid.html">Zone →
600 1.1 christos Tzid table</a> or <a
601 1.6 christos href="https://github.com/unicode-org/cldr/blob/master/common/supplemental/windowsZones.xml"><abbr>XML</abbr>
602 1.1 christos file</a> of the <abbr>CLDR</abbr> data maps proprietary zone IDs
603 1.1 christos to <code><abbr>tz</abbr></code> names.
604 1.3 christos These mappings can be performed programmatically via the <a href="https://github.com/mj1856/TimeZoneConverter">TimeZoneConverter</a> .NET library,
605 1.3 christos or the ICU Java and C++ libraries mentioned <a href="#ICU">above</a>.
606 1.1 christos <li><a
607 1.1 christos href="https://www.oracle.com/java/index.html">Oracle
608 1.1 christos Java</a> contains a copy of a subset of a recent
609 1.1 christos <code><abbr>tz</abbr></code> database in a
610 1.1 christos Java-specific format.</li>
611 1.2 christos <li><a href="https://relativedata.com/page/Time-Zone-Master">Time Zone
612 1.1 christos Master</a> is a Microsoft Windows clock program that can automatically
613 1.4 christos download, compile and use <code><abbr>tz</abbr></code> releases.
614 1.4 christos The Basic version is free.</li>
615 1.1 christos <li><a
616 1.1 christos href="http://veladg.com/velaterra.html">VelaTerra</a> is
617 1.1 christos a macOS program. Its developers
618 1.1 christos <a href="http://veladg.com/tzoffer.html">offer free
619 1.1 christos licenses</a> to <code><abbr>tz</abbr></code> contributors.</li>
620 1.1 christos </ul>
621 1.6 christos </section>
622 1.6 christos
623 1.6 christos <section>
624 1.1 christos <h2 id="other-dbs">Other time zone databases</h2>
625 1.1 christos <ul>
626 1.1 christos <li><a href="https://www.astro.com/atlas">Time-zone Atlas</a>
627 1.4 christos is Astrodienst's Web version of Shanks and Pottenger's out-of-print
628 1.4 christos time zone history atlases
629 1.4 christos <a href="https://www.worldcat.org/oclc/468828649">for the US</a> and
630 1.4 christos <a href="https://www.worldcat.org/oclc/76950459">for the world</a>,
631 1.4 christos now published in <a
632 1.1 christos href="https://astrocom.com/astrology-products/software/acs-atlas-software">software</a>
633 1.1 christos form by <a href="https://astrocom.com">ACS-Starcrafts</a>.
634 1.4 christos Although these extensive atlases
635 1.4 christos <a href="https://astrologynewsservice.com/opinion/how-astrologers-contributed-to-the-information-age-a-brief-history-of-time/">were
636 1.4 christos sources for much of the older <code><abbr>tz</abbr></code> data</a>,
637 1.4 christos they are unreliable as Shanks appears to have
638 1.1 christos guessed many <abbr>UT</abbr> offsets and transitions. The atlases cite no
639 1.1 christos sources and do not indicate which entries are guesswork.</li>
640 1.1 christos <li><a href="https://en.wikipedia.org/wiki/HP-UX">HP-UX</a> has a database in
641 1.1 christos its own <code>tztab</code>(4) format.</li>
642 1.1 christos <li>Microsoft Windows has proprietary data mentioned
643 1.1 christos <a href="#System.TimeZoneInfo">above</a>.</li>
644 1.1 christos <li><a href="https://www.worldtimeserver.com">World Time Server</a>
645 1.1 christos is another time zone database.</li>
646 1.1 christos <li>The <a
647 1.1 christos href="https://www.iata.org/publications/store/Pages/standard-schedules-information.aspx">Standard
648 1.1 christos Schedules Information Manual</a> of the
649 1.1 christos International Air Transport Association
650 1.1 christos gives current time zone rules for airports served by commercial aviation.</li>
651 1.1 christos </ul>
652 1.6 christos </section>
653 1.6 christos
654 1.6 christos <section>
655 1.1 christos <h2 id="maps">Maps</h2>
656 1.1 christos <ul>
657 1.1 christos <li>The <a href="https://www.cia.gov/index.html">United States Central
658 1.1 christos Intelligence Agency (<abbr
659 1.1 christos title="Central Intelligence Agency">CIA</abbr>)</a> publishes a <a
660 1.1 christos href="https://www.cia.gov/library/publications/the-world-factbook/graphics/ref_maps/physical/pdf/standard_time_zones_of_the_world.pdf">time
661 1.1 christos zone map</a>; the
662 1.1 christos <a
663 1.6 christos href="https://legacy.lib.utexas.edu/maps/world.html">Perry–Castañeda
664 1.1 christos Library Map Collection</a>
665 1.1 christos of the University of Texas at Austin has copies of
666 1.1 christos recent editions.
667 1.1 christos The pictorial quality is good,
668 1.1 christos but the maps do not indicate daylight saving time,
669 1.1 christos and parts of the data are a few years out of date.</li>
670 1.6 christos <li><a href="https://www.worldtimezone.com">World Time Zone Map
671 1.6 christos with current time</a>
672 1.1 christos has several fancy time zone maps; it covers Russia particularly well.
673 1.1 christos The maps' pictorial quality is not quite as good as the
674 1.1 christos <abbr>CIA</abbr>'s
675 1.1 christos but the maps are more up to date.</li>
676 1.1 christos <li><a
677 1.1 christos href="https://blog.poormansmath.net/how-much-is-time-wrong-around-the-world/">How
678 1.1 christos much is time wrong around the world?</a> maps the difference between
679 1.1 christos mean solar and standard time, highlighting areas such as western China
680 1.1 christos where the two differ greatly. It's a bit out of date, unfortunately.</li>
681 1.1 christos </ul>
682 1.6 christos </section>
683 1.6 christos
684 1.6 christos <section>
685 1.1 christos <h2 id="boundaries">Time zone boundaries</h2>
686 1.2 christos <p>Geographical boundaries between timezones are available
687 1.1 christos from several <a href="https://en.wikipedia.org/wiki/Geolocation">geolocation</a>
688 1.1 christos services and other sources.</p>
689 1.1 christos <ul>
690 1.1 christos <li><a href="https://github.com/evansiroky/timezone-boundary-builder">Timezone
691 1.1 christos Boundary Builder</a> extracts
692 1.1 christos <a href="https://www.openstreetmap.org">Open Street Map</a> data to build
693 1.2 christos boundaries of <code><abbr>tzdb</abbr></code> timezones.
694 1.1 christos Its code is freely available under the <abbr>MIT</abbr> license, and
695 1.1 christos its data entries are freely available under the
696 1.1 christos <a href="https://opendatacommons.org/licenses/odbl/">Open Data Commons
697 1.1 christos Open Database License</a>. The maps' borders appear to be quite accurate.</li>
698 1.1 christos <li>Programmatic interfaces that map geographical coordinates via tz_world to
699 1.2 christos <code><abbr>tzdb</abbr></code> timezones include:
700 1.1 christos <ul>
701 1.1 christos <li><a href="https://github.com/mj1856/GeoTimeZone">GeoTimeZone</a> is
702 1.1 christos written in <a
703 1.1 christos href="https://en.wikipedia.org/wiki/C_Sharp_(programming_language)">C#</a>
704 1.1 christos and is freely available under the <abbr>MIT</abbr> license.</li>
705 1.1 christos <li>The <a href="https://github.com/bradfitz/latlong">latlong package</a>
706 1.1 christos is written in Go and is freely available under the Apache License.</li>
707 1.1 christos <li><a href="https://github.com/drtimcooper/LatLongToTimezone">LatLongToTimezone</a>,
708 1.1 christos in both Java and
709 1.1 christos <a href="https://en.wikipedia.org/wiki/Swift_(programming_language)">Swift</a>
710 1.1 christos form, is freely available under the MIT license.</li>
711 1.1 christos <li>For <a href="https://nodejs.org/en/">Node.js</a>,
712 1.1 christos the <a href="https://www.npmjs.com/package/geo-tz">geo-tz module</a>
713 1.1 christos is freely available under the MIT license, and
714 1.1 christos the <a href="https://www.npmjs.com/package/tz-lookup">tz-lookup module</a>
715 1.1 christos is in the public domain.</li>
716 1.1 christos <li>The <a
717 1.1 christos href="https://github.com/MrMinimal64/timezonefinder">timezonefinder</a>
718 1.1 christos library for Python is freely available under the MIT license.
719 1.1 christos <li>The <a
720 1.1 christos href="https://github.com/gunyarakun/timezone_finder">timezone_finder</a>
721 1.1 christos library for Ruby is freely available under the MIT license.</li>
722 1.1 christos </ul></li>
723 1.1 christos <li>Free access via a network API, if you register a key, is provided by
724 1.4 christos the <a
725 1.4 christos href="https://www.geonames.org/export/web-services.html#timezone">GeoNames
726 1.4 christos Timezone web service</a>, the <a
727 1.4 christos href="https://developers.google.com/maps/documentation/timezone/intro">Google
728 1.4 christos Maps Time Zone API</a>, and
729 1.1 christos the <a href="https://timezonedb.com">Time Zone Database & API</a>.
730 1.1 christos Commercial network API access is provided
731 1.1 christos by <a href="https://askgeo.com">AskGeo</a>
732 1.1 christos and <a href="https://www.geogarage.com/blog/news-1/post/geogarage-time-zone-api-31">GeoGarage</a>.
733 1.1 christos </li>
734 1.1 christos <li>"<a
735 1.1 christos href="https://stackoverflow.com/questions/16086962/how-to-get-a-time-zone-from-a-location-using-latitude-and-longitude-coordinates/16086964">How
736 1.1 christos to get a time zone from a location using latitude and longitude
737 1.1 christos coordinates?</a>" discusses other geolocation possibilities.</li>
738 1.1 christos <li><a href="http://statoids.com/statoids.html">Administrative
739 1.1 christos Divisions of Countries ("Statoids")</a> lists
740 1.1 christos political subdivision data related to time zones.</li>
741 1.1 christos <li><a href="http://home.kpn.nl/vanadovv/time/Multizones.html">Time
742 1.1 christos zone boundaries for multizone countries</a> summarizes legal
743 1.1 christos boundaries between time zones within countries.</li>
744 1.1 christos <li><a href="http://manifold.net/info/freestuff.shtml">Manifold Software
745 1.1 christos – GIS and Database Tools</a> includes a Manifold-format map of
746 1.1 christos world time zone boundaries distributed under the
747 1.1 christos <abbr>GPL</abbr>.</li>
748 1.1 christos <li>A ship within the <a
749 1.1 christos href="https://en.wikipedia.org/wiki/Territorial_waters">territorial
750 1.1 christos waters</a> of any nation uses that nation's time. In international
751 1.1 christos waters, time zone boundaries are meridians 15° apart, except that
752 1.1 christos <abbr>UT</abbr>−12 and <abbr>UT</abbr>+12 are each 7.5°
753 1.1 christos wide and are separated by
754 1.1 christos the 180° meridian (not by the International Date Line, which is
755 1.1 christos for land and territorial waters only). A captain can change ship's
756 1.1 christos clocks any time after entering a new time zone; midnight changes are
757 1.1 christos common.</li>
758 1.1 christos </ul>
759 1.6 christos </section>
760 1.6 christos
761 1.6 christos <section>
762 1.1 christos <h2 id="civil">Civil time concepts and history</h2>
763 1.1 christos <ul>
764 1.1 christos <li><a href="https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time">A
765 1.1 christos Walk through Time</a>
766 1.1 christos surveys the evolution of timekeeping.</li>
767 1.4 christos <li>The history of daylight saving time is surveyed in <a
768 1.4 christos href="http://www.webexhibits.org/daylightsaving/">About Daylight
769 1.4 christos Saving Time – History, rationale, laws & dates</a> and summarized in
770 1.4 christos <a href="http://seizethedaylight.com/dst/">A Brief
771 1.4 christos History of Daylight Saving Time</a>.</li>
772 1.4 christos <li><a href="https://www.laphamsquarterly.org/roundtable/time-lords">Time
773 1.4 christos Lords</a> discusses how authoritarians manipulate civil time.</li>
774 1.1 christos <li><a href="https://www.w3.org/TR/timezone/">Working with Time Zones</a>
775 1.1 christos contains guidelines and best practices for software applications that
776 1.1 christos deal with civil time.</li>
777 1.1 christos <li><a href="https://www.staff.science.uu.nl/~gent0113/idl/idl.htm">A History of
778 1.1 christos the International Date Line</a> tells the story of the most important
779 1.1 christos time zone boundary.</li>
780 1.1 christos <li><a href="http://statoids.com/tconcept.html">Basic Time
781 1.1 christos Zone Concepts</a> discusses terminological issues behind time zones.</li>
782 1.1 christos </ul>
783 1.6 christos </section>
784 1.6 christos
785 1.6 christos <section>
786 1.1 christos <h2 id="national">National histories of legal time</h2>
787 1.1 christos <dl>
788 1.1 christos <dt>Australia</dt>
789 1.6 christos <dd>The Parliamentary Library commissioned a <a
790 1.1 christos href="https://www.aph.gov.au/binaries/library/pubs/rp/2009-10/10rp10.pdf">research
791 1.1 christos paper on daylight saving time in Australia</a>.
792 1.1 christos The Bureau of Meteorology publishes a list of <a
793 1.1 christos href="http://www.bom.gov.au/climate/averages/tables/dst_times.shtml">Implementation
794 1.1 christos Dates of Daylight Savings Time within Australia</a>.</dd>
795 1.1 christos <dt>Belgium</dt>
796 1.1 christos <dd>The Royal Observatory of Belgium maintains a table of <a
797 1.4 christos href="https://www.astro.oma.be/GENERAL/INFO/nli001a.html"
798 1.1 christos hreflang="nl">time in Belgium (in Dutch)</a>.</dd>
799 1.1 christos <dt>Brazil</dt>
800 1.1 christos <dd>The Time Service Department of the National Observatory
801 1.1 christos records <a href="http://pcdsh01.on.br/DecHV.html"
802 1.1 christos hreflang="pt-BR">Brazil's daylight saving time decrees (in
803 1.1 christos Portuguese)</a>.</dd>
804 1.1 christos <dt>Canada</dt>
805 1.1 christos <dd>National Research Council Canada publishes current
806 1.1 christos and some older information about <a
807 1.6 christos href="https://nrc.canada.ca/en/certifications-evaluations-standards/canadas-official-time/time-zones-daylight-saving-time">time
808 1.6 christos zones and daylight saving time</a>.</dd>
809 1.1 christos <dt>Chile</dt>
810 1.1 christos <dd>The Hydrographic and Oceanographic Service of the Chilean Navy publishes a
811 1.4 christos <a href="https://www.horaoficial.cl/historia_hora.html" hreflang="es">history of
812 1.1 christos Chile's official time (in Spanish)</a>.</dd>
813 1.3 christos <dt>China</dt>
814 1.3 christos <dd>The Hong Kong Observatory maintains a
815 1.3 christos <a href="https://www.hko.gov.hk/gts/time/Summertime.htm">history of
816 1.3 christos summer time in Hong Kong</a>,
817 1.3 christos and Macau's Meteorological and Geophysical Bureau maintains a <a
818 1.3 christos href="http://www.smg.gov.mo/smg/geophysics/e_t_Summer%20Time.htm">similar
819 1.3 christos history for Macau</a>.
820 1.3 christos Unfortunately the latter is incomplete and has errors.</dd>
821 1.1 christos <dt>Czech Republic</dt>
822 1.1 christos <dd><a href="https://kalendar.beda.cz/kdy-zacina-a-konci-letni-cas"
823 1.1 christos hreflang="cs">When daylight saving time starts and ends (in Czech)</a>
824 1.1 christos summarizes and cites historical DST regulations.</dd>
825 1.1 christos <dt>Germany</dt>
826 1.1 christos <dd>The National Institute for Science and Technology maintains the <a
827 1.1 christos href="https://www.ptb.de/cms/en/fachabteilungen/abt4/fb-44/ag-441/realisation-of-legal-time-in-germany.html">Realisation
828 1.1 christos of Legal Time in Germany</a>.</dd>
829 1.1 christos <dt>Israel</dt>
830 1.1 christos <dd>The Interior Ministry periodically issues <a
831 1.1 christos href="ftp://ftp.cs.huji.ac.il/pub/tz/announcements"
832 1.1 christos hreflang="he">announcements (in Hebrew)</a>.</dd>
833 1.1 christos <dt>Italy</dt>
834 1.6 christos <dd>The National Institute of Metrological Research publishes a
835 1.4 christos <a href="http://oldsite.inrim.it/res/tf/ora_legale_i.shtml" hreflang="it">table
836 1.4 christos of civil time (in Italian)</a>.</dd>
837 1.2 christos <dt>Malaysia</dt>
838 1.2 christos <dd>See Singapore <a href="#Singapore">below</a>.</dd>
839 1.1 christos <dt>Mexico</dt>
840 1.1 christos <dd>The Investigation and Analysis Service of the Mexican Library of
841 1.1 christos Congress has published a <a
842 1.1 christos href="http://www.diputados.gob.mx/bibliot/publica/inveyana/polisoc/horver/index.htm"
843 1.1 christos hreflang="es">history of Mexican local time (in Spanish)</a>.</dd>
844 1.1 christos <dt>Netherlands</dt>
845 1.1 christos <dd><a href="https://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm"
846 1.1 christos hreflang="nl">Legal time in the Netherlands (in Dutch)</a>
847 1.1 christos covers the history of local time in the Netherlands from ancient times.</dd>
848 1.1 christos <dt>New Zealand</dt>
849 1.1 christos <dd>The Department of Internal Affairs maintains a brief <a
850 1.1 christos href="https://www.dia.govt.nz/Daylight-Saving-History">History of
851 1.6 christos Daylight Saving</a>.</dd>
852 1.1 christos <dt>Singapore</dt>
853 1.1 christos <dd><a id="Singapore"
854 1.6 christos href="http://www.math.nus.edu.sg/~mathelmr/teaching/timezone.html">Why
855 1.1 christos is Singapore in the "Wrong" Time Zone?</a> details the
856 1.1 christos history of legal time in Singapore and Malaysia.</dd>
857 1.1 christos <dt>United Kingdom</dt>
858 1.1 christos <dd><a
859 1.1 christos href="https://www.polyomino.org.uk/british-time/">History of
860 1.1 christos legal time in Britain</a> discusses in detail the country
861 1.6 christos with perhaps the best-documented history of clock adjustments.</dd>
862 1.1 christos <dt>United States</dt>
863 1.1 christos <dd>The Department of Transportation's <a
864 1.1 christos href="https://www.transportation.gov/regulations/recent-time-zone-proceedings">Recent
865 1.1 christos Time Zone Proceedings</a> lists changes to time zone boundaries.</dd>
866 1.1 christos <dt>Uruguay</dt>
867 1.1 christos <dd>The Oceanography, Hydrography, and Meteorology Service of the Uruguayan
868 1.1 christos Navy (SOHMA) publishes an annual <a
869 1.6 christos href="http://www.armada.gub.uy/sohma/index.php/servicios/datos-astronomicos" hreflang="es">almanac
870 1.1 christos (in Spanish)</a>.</dd>
871 1.1 christos </dl>
872 1.6 christos </section>
873 1.6 christos
874 1.6 christos <section>
875 1.1 christos <h2 id="precision">Precision timekeeping</h2>
876 1.1 christos <ul>
877 1.1 christos <li><a
878 1.1 christos href="http://leapsecond.com/hpan/an1289.pdf">The
879 1.1 christos Science of Timekeeping</a> is a thorough introduction
880 1.1 christos to the theory and practice of precision timekeeping.</li>
881 1.1 christos <li><a href="https://doi.org/10.1007/978-3-319-59909-0">The Science of
882 1.1 christos Time 2016</a> contains several freely-readable papers.</li>
883 1.1 christos <li><a href="http://www.ntp.org"><abbr
884 1.1 christos title="Network Time Protocol">NTP</abbr>: The Network
885 1.1 christos Time Protocol</a> (Internet <abbr>RFC</abbr> 5905)
886 1.1 christos discusses how to synchronize clocks of
887 1.1 christos Internet hosts.</li>
888 1.2 christos <li>The <a href="https://www.usenix.org/system/files/conference/nsdi18/nsdi18-geng.pdf"><span style="font-variant: small-caps">Huygens</span></a>
889 1.2 christos family of software algorithms can achieve accuracy to a few tens of
890 1.2 christos nanoseconds in scalable server farms without special hardware.</li>
891 1.1 christos <li>The <a
892 1.1 christos href="https://www.nist.gov/intelligent-systems-division/ieee-1588">Precision
893 1.1 christos Time Protocol</a> (<abbr
894 1.1 christos title="Institute of Electrical and Electronics Engineers">IEEE</abbr> 1588)
895 1.2 christos can achieve submicrosecond clock accuracy on a local area network
896 1.2 christos with special-purpose hardware.</li>
897 1.1 christos <li><a
898 1.1 christos href="https://tools.ietf.org/html/rfc4833">Timezone
899 1.1 christos Options for <abbr title="Dynamic Host Configuration Protocol">DHCP</abbr></a>
900 1.1 christos (Internet <abbr>RFC</abbr> 4833)
901 1.1 christos specifies a <a
902 1.1 christos href="https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol"><abbr>DHCP</abbr></a>
903 1.1 christos option for a server to configure
904 1.1 christos a client's time zone and daylight saving settings automatically.</li>
905 1.1 christos <li><a
906 1.1 christos href="https://www.cv.nrao.edu/~rfisher/Ephemerides/times.html">Astronomical
907 1.1 christos Times</a> explains more abstruse astronomical time scales like
908 1.1 christos <abbr title="Terrestrial Dynamic Time">TDT</abbr>,
909 1.1 christos <abbr title="Geocentric Coordinate Time">TCG</abbr>, and
910 1.1 christos <abbr title="Barycentric Dynamic Time">TDB</abbr>.
911 1.1 christos <a href="https://www.ucolick.org/~sla/leapsecs/timescales.html">Time
912 1.1 christos Scales</a> goes into more detail, particularly for historical variants.</li>
913 1.1 christos <li>The <a href="https://www.iau.org"><abbr
914 1.1 christos title="International Astronomical Union">IAU</abbr></a>'s <a
915 1.1 christos href="http://www.iausofa.org"><abbr
916 1.1 christos title="Standards Of Fundamental Astronomy">SOFA</abbr></a>
917 1.1 christos collection contains C and <a
918 1.1 christos href="https://en.wikipedia.org/wiki/Fortran">Fortran</a>
919 1.1 christos code for converting among time scales like
920 1.1 christos <abbr title="International Atomic Time">TAI</abbr>,
921 1.1 christos <abbr>TDB</abbr>, <abbr>TDT</abbr> and
922 1.1 christos <abbr>UTC</abbr>.</li>
923 1.1 christos <li><a
924 1.1 christos href="https://www.giss.nasa.gov/tools/mars24/help/notes.html">Mars24 Sunclock
925 1.1 christos – Time on Mars</a> describes Airy Mean Time (<abbr>AMT</abbr>) and the
926 1.1 christos diverse local time
927 1.1 christos scales used by each landed mission on Mars.</li>
928 1.1 christos <li><a href="http://leapsecond.com">LeapSecond.com</a> is
929 1.1 christos dedicated not only to leap seconds but to precise time and frequency
930 1.1 christos in general. It covers the state of the art in amateur timekeeping, and
931 1.1 christos how the art has progressed over the past few decades.</li>
932 1.1 christos <li><a
933 1.1 christos href="https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html"><abbr
934 1.1 christos title="International Earth Rotation and Reference Systems Service">IERS</abbr>
935 1.1 christos Bulletins</a> contains official publications of the International
936 1.1 christos Earth Rotation and Reference Systems Service, which decides when leap
937 1.4 christos seconds occur. The <code><abbr>tz</abbr></code> code and data support leap seconds
938 1.1 christos via an optional "<code>right</code>" configuration, as opposed to the
939 1.1 christos default "<code>posix</code>" configuration.</li>
940 1.1 christos <li><a href="https://developers.google.com/time/smear">Leap Smear</a>
941 1.1 christos discusses how to gradually adjust <abbr>POSIX</abbr> clocks near a
942 1.1 christos leap second so that they disagree with <abbr>UTC</abbr> by at most a
943 1.1 christos half second, even though every <abbr>POSIX</abbr> minute has exactly
944 1.4 christos sixty seconds. This approach works with the default <code><abbr>tz</abbr></code>
945 1.1 christos "<code>posix</code>" configuration, is <a
946 1.1 christos href="http://bk1.ntp.org/ntp-stable/README.leapsmear">supported</a> by
947 1.1 christos the <abbr>NTP</abbr> reference implementation, and is used by major
948 1.1 christos cloud service providers.</li>
949 1.1 christos <li>The <a
950 1.1 christos href="https://pairlist6.pair.net/mailman/listinfo/leapsecs">Leap
951 1.1 christos Second Discussion List</a> covers <a
952 1.1 christos href="https://www2.unb.ca/gge/Resources/gpsworld.november99.pdf">McCarthy
953 1.1 christos and Klepczynski's 1999 proposal to discontinue leap seconds</a>,
954 1.1 christos discussed further in
955 1.1 christos <a href="https://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf">The
956 1.1 christos leap second: its history and possible future</a>.
957 1.1 christos <a href="https://www.ucolick.org/~sla/leapsecs/"><abbr>UTC</abbr>
958 1.1 christos might be redefined
959 1.1 christos without Leap Seconds</a> gives pointers on this
960 1.1 christos contentious issue, which was active until 2015 and could become active
961 1.1 christos again.</li>
962 1.1 christos </ul>
963 1.6 christos </section>
964 1.6 christos
965 1.6 christos <section>
966 1.1 christos <h2 id="notation">Time notation</h2>
967 1.1 christos <ul>
968 1.1 christos <li>The <a id="CLDR" href="http://cldr.unicode.org">Unicode Common Locale Data
969 1.1 christos Repository (<abbr>CLDR</abbr>) Project</a> has localizations for time
970 1.1 christos zone names, abbreviations, identifiers, and formats. For example, it
971 1.1 christos contains French translations for "Eastern European Summer Time",
972 1.1 christos "<abbr title="Eastern European Summer Time">EEST</abbr>", and
973 1.1 christos "Bucharest". Its
974 1.1 christos <a href="https://unicode.org/cldr/charts/latest/by_type/">by-type
975 1.1 christos charts</a> show these values for many locales. Data values are available in
976 1.1 christos both <abbr title="Locale Data Markup Language">LDML</abbr>
977 1.1 christos (an <abbr>XML</abbr> format) and <abbr>JSON</abbr>.
978 1.1 christos <li>
979 1.1 christos <a href="https://www.cl.cam.ac.uk/~mgk25/iso-time.html">A summary of
980 1.6 christos the international standard date and time notation</a> covers
981 1.1 christos <a
982 1.6 christos href="https://www.iso.org/standard/70907.html"><em><abbr
983 1.6 christos title="International Organization for Standardization">ISO</abbr>
984 1.6 christos 8601-1:2019 – Date and time – Representations for information
985 1.6 christos interchange – Part 1: Basic rules</em></a>.</li>
986 1.1 christos <li>
987 1.6 christos <a href="https://www.w3.org/TR/xmlschema/#dateTime"><abbr>XML</abbr>
988 1.1 christos Schema: Datatypes – dateTime</a> specifies a format inspired by
989 1.1 christos <abbr>ISO</abbr> 8601 that is in common use in <abbr>XML</abbr> data.</li>
990 1.1 christos <li><a href="https://tools.ietf.org/html/rfc5322#section-3.3">§3.3 of
991 1.1 christos Internet Message Format</a> (Internet <abbr>RFC</abbr> 5322)
992 1.1 christos specifies the time notation used in email and <a
993 1.1 christos href="https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol"><abbr>HTTP</abbr></a>
994 1.1 christos headers.</li>
995 1.1 christos <li>
996 1.1 christos <a href="https://tools.ietf.org/html/rfc3339">Date and Time
997 1.1 christos on the Internet: Timestamps</a> (Internet <abbr>RFC</abbr> 3339)
998 1.1 christos specifies an <abbr>ISO</abbr> 8601
999 1.1 christos profile for use in new Internet
1000 1.1 christos protocols.</li>
1001 1.1 christos <li>
1002 1.1 christos <a href="https://www.hackcraft.net/web/datetime/">Date & Time
1003 1.1 christos Formats on the Web</a> surveys web- and Internet-oriented date and time
1004 1.1 christos formats.</li>
1005 1.1 christos <li>Alphabetic time zone abbreviations should not be used as unique
1006 1.1 christos identifiers for <abbr>UT</abbr> offsets as they are ambiguous in
1007 1.1 christos practice. For example, in English-speaking North America
1008 1.1 christos "<abbr>CST</abbr>" denotes 6 hours behind <abbr>UT</abbr>,
1009 1.1 christos but in China it denotes 8 hours ahead of <abbr>UT</abbr>,
1010 1.1 christos and French-speaking North Americans prefer
1011 1.1 christos "<abbr title="Heure Normale du Centre">HNC</abbr>" to
1012 1.1 christos "<abbr>CST</abbr>". The <code><abbr>tz</abbr></code>
1013 1.2 christos database contains English abbreviations for many timestamps;
1014 1.1 christos unfortunately some of these abbreviations were merely the database maintainers'
1015 1.1 christos inventions, and these have been removed when possible.</li>
1016 1.1 christos <li>Numeric time zone abbreviations typically count hours east of
1017 1.1 christos <abbr>UT</abbr>, e.g., +09 for Japan and
1018 1.1 christos −10 for Hawaii. However, the <abbr>POSIX</abbr>
1019 1.1 christos <code><abbr>TZ</abbr></code> environment variable uses the opposite convention.
1020 1.1 christos For example, one might use <code><abbr>TZ</abbr>="<abbr
1021 1.1 christos title="Japan Standard Time">JST</abbr>-9"</code> and
1022 1.1 christos <code><abbr>TZ</abbr>="<abbr title="Hawaii Standard Time">HST</abbr>10"</code>
1023 1.1 christos for Japan and Hawaii, respectively. If the
1024 1.1 christos <code><abbr>tz</abbr></code> database is available, it is usually better to use
1025 1.1 christos settings like <code><abbr>TZ</abbr>="Asia/Tokyo"</code> and
1026 1.1 christos <code><abbr>TZ</abbr>="Pacific/Honolulu"</code> instead, as this should avoid
1027 1.2 christos confusion, handle old timestamps better, and insulate you better from
1028 1.1 christos any future changes to the rules. One should never set
1029 1.1 christos <abbr>POSIX</abbr> <code><abbr>TZ</abbr></code> to a value like
1030 1.1 christos <code>"GMT-9"</code>, though, since this would incorrectly imply that
1031 1.1 christos local time is nine hours ahead of <abbr>UT</abbr> and the time zone
1032 1.1 christos is called "<abbr>GMT</abbr>".</li>
1033 1.1 christos </ul>
1034 1.6 christos </section>
1035 1.6 christos
1036 1.6 christos <section>
1037 1.1 christos <h2 id="see-also">See also</h2>
1038 1.1 christos <ul>
1039 1.1 christos <li><a href="theory.html">Theory and pragmatics of the tz code and data</a></li>
1040 1.1 christos <li><a href="tz-art.html">Time and the Arts</a></li>
1041 1.1 christos </ul>
1042 1.6 christos </section>
1043 1.6 christos
1044 1.6 christos <footer>
1045 1.1 christos <hr>
1046 1.1 christos This web page is in the public domain, so clarified as of
1047 1.1 christos 2009-05-17 by Arthur David Olson.
1048 1.1 christos <br>
1049 1.1 christos Please send corrections to this web page to the
1050 1.1 christos <a href="mailto:tz (a] iana.org">time zone mailing list</a>.
1051 1.6 christos </footer>
1052 1.1 christos </body>
1053 1.1 christos </html>
1054