649 lines
31 KiB
HTML
649 lines
31 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>Sources for Time Zone and Daylight Saving Time Data</title>
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<link rel="schema.DC" href="http://purl.org/DC/elements/1.1/">
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<meta http-equiv="Content-type" content='text/html; charset="US-ASCII"'>
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<meta name="DC.Creator" content="Eggert, Paul">
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<meta name="DC.Contributor" content="Olson, Arthur David">
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<meta name="DC.Date" content="2007-12-26">
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<meta name="DC.Description"
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content="Sources of information about time zones and daylight saving time">
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<meta name="DC.Identifier" content="http://www.twinsun.com/tz/tz-link.htm">
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<meta name="Keywords"
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content="database,daylight saving,DST,time zone,timezone,tz,zoneinfo">
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</head>
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<body>
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<h1>Sources for Time Zone and Daylight Saving Time Data</h1>
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<address>
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@(#)tz-link.htm 8.22
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</address>
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<p>
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This file is in the public domain, so clarified as of
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2009-05-17 by Arthur David Olson.
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</p>
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<p>
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Please send corrections to this web page to the
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<a href="mailto:tz@elsie.nci.nih.gov">time zone mailing list</a>.</p>
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<h2>The <code>tz</code> database</h2>
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<p>
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The <a href="http://en.wikipedia.org/wiki/Public_domain">public-domain</a>
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time zone database contains code and data
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that represent the history of local time
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for many representative locations around the globe.
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It is updated periodically to reflect changes made by political bodies
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to <a href="http://en.wikipedia.org/wiki/Time_zone">time zone</a>
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boundaries, <a
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href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time"><abbr
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title="Coordinated Universal Time">UTC</abbr></a> offsets, and
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<a href="http://en.wikipedia.org/wiki/Daylight_saving">daylight-saving</a>
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rules.
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This database (often called <code>tz</code> or <a
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href="http://en.wikipedia.org/wiki/Zoneinfo"><code>zoneinfo</code></a>)
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is used by several implementations,
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including
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<a href="http://www.gnu.org/software/libc/">the
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<abbr title="GNU's Not Unix">GNU</abbr>
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C Library</a> used in
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<a href="http://www.linux.org/"><abbr>GNU</abbr>/Linux</a>,
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<a href="http://www.freebsd.org/">FreeBSD</a>,
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<a href="http://netbsd.org/">NetBSD</a>,
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<a href="http://openbsd.org/">OpenBSD</a>,
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<a href="http://cygwin.com/">Cygwin</a>,
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<a href="http://www.delorie.com/djgpp/"><abbr
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title="DJ's GNU Programming Platform">DJGPP</abbr></a>,
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<a href="http://ibm.com/aix">AIX</a>,
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<a href="http://www.apple.com/macosx/">Mac OS X</a>,
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<a href="http://h71000.www7.hp.com/">OpenVMS</a>,
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<a href="http://oracle.com/database">Oracle Database</a>,
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<a href="http://sun.com/software/solaris">Solaris</a>,
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<a href="http://h30097.www3.hp.com/">Tru64</a>, and
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<a href="http://sco.com/products/unixware">UnixWare</a>.</p>
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<p>
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Each location in the database represents a national region where all
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clocks keeping local time have agreed since 1970.
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Locations are identified by continent or ocean and then by the name of
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the location, which is typically the largest city within the region.
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For example, <code>America/New_York</code>
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represents most of the <abbr title="United States">US</abbr> eastern time zone;
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<code>America/Phoenix</code> represents most of Arizona, which
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uses mountain time without daylight saving time (<abbr
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title="daylight saving time">DST</abbr>);
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<code>America/Detroit</code> represents most of Michigan, which uses
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eastern time but with different <abbr>DST</abbr> rules in 1975;
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and other entries represent smaller regions like Starke County,
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Indiana, which switched from central to eastern time in 1991
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and switched back in 2006.
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To use the database on an extended <a
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href="http://en.wikipedia.org/wiki/POSIX"><abbr
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title="Portable Operating System Interface">POSIX</abbr></a>
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implementation set the <code>TZ</code> environment variable to
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the location's full name, e.g., <code>TZ="America/New_York"</code>.</p>
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<p>
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In the <code>tz</code> database's
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<a href="ftp://elsie.nci.nih.gov/pub"><abbr
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title="File Transfer Protocol">FTP</abbr> distribution</a>
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the code is in the file <code>tzcode<var>C</var>.tar.gz</code>,
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where <code><var>C</var></code> is the code's version;
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similarly, the data are in <code>tzdata<var>D</var>.tar.gz</code>,
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where <code><var>D</var></code> is the data's version.
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The following <a
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href="http://en.wikipedia.org/wiki/Unix_shell">shell</a> commands download
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these files to a <abbr>GNU</abbr>/Linux or similar host;
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see the downloaded
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<code>README</code> file for what to do next.</p>
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<pre style="margin-left: 2em"><code><a href="http://www.gnu.org/software/wget/">wget</a> 'ftp://elsie.nci.nih.gov/pub/tz*.tar.gz'
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<a href="http://www.gnu.org/software/gzip/">gzip</a> -dc tzcode*.tar.gz | <a href="http://www.gnu.org/software/tar/">tar</a> -xf -
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gzip -dc tzdata*.tar.gz | tar -xf -
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</code></pre>
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<p>
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The code lets you compile the <code>tz</code> source files into
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machine-readable binary files, one for each location. It also lets
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you read a <code>tz</code> binary file and interpret time stamps for that
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location.</p>
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<p>
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The data are by no means authoritative. If you find errors, please
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send changes to the <a href="mailto:tz@elsie.nci.nih.gov">time zone
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mailing list</a>. You can also <a
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href="http://news.gmane.org/gmane.comp.time.tz">browse recent
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messages</a> sent to the mailing list, <a
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href="mailto:tz-request@elsie.nci.nih.gov">subscribe</a> to it,
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retrieve the <a
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href="ftp://elsie.nci.nih.gov/pub/tzarchive.gz">full archive of old
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messages</a> (in gzip compressed format), or retrieve <a
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href="ftp://munnari.oz.au/pub/oldtz">archived older versions of code
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and data</a>.</p>
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<p>
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The Web has several other sources for time zone and daylight saving time data.
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Here are some recent links that may be of interest.
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</p>
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<h2>Web pages using recent versions of the <code>tz</code> database</h2>
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<p>
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These are listed roughly in ascending order of complexity and fanciness.
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</p>
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<ul>
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<li><a href="http://twiki.org/cgi-bin/xtra/tzdatepick.html">Date and Time Gateway</a>
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lets you see the <code>TZ</code> values directly.</li>
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<li><a
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href="http://convertit.com/Go/ConvertIt/World_Time/Current_Time.ASP">Current
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Time in 1000 Places</a> uses descriptions of the values.</li>
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<li><a href="http://www.timezoneconverter.com/">Time Zone Converter</a>
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uses a pulldown menu.</li>
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<li><a href="http://home.tiscali.nl/~t876506/TZworld.html">Complete
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timezone information for all countries</a> displays tables of DST rules.
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<li><a href="http://timeanddate.com/worldclock/">The World Clock -
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Time Zones</a> lets you sort zone names and convert times.</li>
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<li><a href="http://daylight-savings-time.info/">Graphical Display of
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Time Zones and Daylight Saving Times</a> shows a graph of time
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difference versus time for any pair of locations.</li>
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<li>The <a href="http://worldtimeengine.com/">World Time Engine</a>
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also contains data about time zone boundaries; it supports queries via place
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names and shows location maps.</li>
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</ul>
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<h2>Other time zone database formats</h2>
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<ul>
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<li>The <a href="ftp://ftp.rfc-editor.org/in-notes/rfc2445.txt">
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Internet Calendaring and Scheduling Core Object Specification
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(iCalendar)</a>, Internet <abbr title="Request For
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Comments">RFC</abbr> 2445, published by the (now-concluded) <a
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href="http://ietf.org/html.charters/OLD/calsch-charter.html"><abbr
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title="Internet Engineering Task Force">IETF</abbr>
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Calendaring and Scheduling Working Group (<abbr
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title="Calendaring and Scheduling Working Group">calsch</abbr>)</a>
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covers time zone
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data; see its VTIMEZONE calendar component.
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The <a href="http://calconnect.org/">Calendaring and Scheduling
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Consortium</a> is promoting further work in this area. <a
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href="http://calconnect.org/publications/icalendartimezoneproblemsandrecommendationsv1.0.pdf">iCalendar
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TIMEZONE Problems and Recommendations</a> offers guidelines and
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recommendations for the use of VTIMEZONE and <code>tz</code>.</li>
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<li><a href="http://calconnect.org/dstlinks.shtml">Extended Daylight
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Saving Time Links, Advisories and Changes</a> lists vendor material on recent
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daylight saving time changes.</li>
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<li><a
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href="http://calconnect.org/publications/timezoneregistryandservicerecommendationsv1.0.pdf">Timezone
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Registry and Service Recommendations</a> discusses a
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strategy for defining and deploying a time zone
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registration process that would establish unique names for each
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version of each <code>tz</code> zone, along with a polygonal
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representation of the geographical area corresponding to the
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zone.</li>
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<li>The <a
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href="http://lists.w3.org/Archives/Public/www-rdf-calendar/">www-rdf-calendar</a>
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list discusses <a
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href="http://www.w3.org/RDF/"><abbr
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title="Resource Description Framework">RDF</abbr></a>-based calendar
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and group scheduling systems, and has a <a
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href="http://www.w3.org/2002/12/cal/#tzd">workspace on time zone
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data</a> converted from <code>tz</code>. An earlier <a
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href="http://www.w3.org/2000/01/foo">schema</a> was sketched out.</li>
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</ul>
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<h2>Other <code>tz</code> compilers</h2>
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<ul>
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<li><a href="http://www.dachaplin.dsl.pipex.com/vzic/">Vzic iCalendar
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Timezone Converter</a> describes a <a
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href="http://en.wikipedia.org/wiki/C_%28programming_language%29">C</a>
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program that compiles
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<code>tz</code> source into iCalendar-compatible VTIMEZONE files.
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Vzic is freely
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available under the <a
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href="http://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr>
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General Public License (<abbr
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title="General Public License">GPL</abbr>)</a>.</li>
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<li><a href="http://sourceforge.net/projects/tzical">tziCal - tz
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database conversion utility</a> is like Vzic, except for the <a
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href="http://msdn.microsoft.com/netframework">.NET framework</a>.</li>
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<li><a
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href="http://search.cpan.org/dist/DateTime-TimeZone/">DateTime::TimeZone</a>
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contains a script <code>parse_olson</code> that compiles
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<code>tz</code> source into <a href="http://www.perl.org/">Perl</a>
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modules. It is part of the Perl <a
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href="http://datetime.perl.org/">DateTime Project</a>, which is freely
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available under both the <abbr>GPL</abbr> and the Perl Artistic
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License. DateTime::TimeZone also contains a script
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<code>tests_from_zdump</code> that generates test cases for each clock
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transition in the <code>tz</code> database.</li>
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<li><a href="http://icu-project.org/">International Components for
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Unicode (<abbr>ICU</abbr>)</a> contains C/C++ and <a
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href="http://en.wikipedia.org/wiki/Java_%28programming_language%29">Java</a>
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libraries for internationalization that
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has a compiler from <code>tz</code> source
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into an <abbr>ICU</abbr>-specific format.
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<abbr>ICU</abbr> is freely available under a
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<abbr title="Berkeley Software Distribution">BSD</abbr>-style license.</li>
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<li><a href="http://joda-time.sourceforge.net/">Joda Time - Java date
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and time <abbr title="Application Program Interface">API</abbr></a>
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contains a class
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<code>org.joda.time.tz.ZoneInfoCompiler</code> that compiles
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<code>tz</code> source into a Joda-specific binary format. Joda Time
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is freely available under a <abbr>BSD</abbr>-style license.</li>
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<li><a href="http://pytz.sourceforge.net">PyTZ - Python Time
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Zone Library</a> compiles <code>tz</code> source into
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<a href="http://python.org/">Python</a>.
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It is freely available under a <abbr>BSD</abbr>-style license.</li>
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<li><a href="http://tzinfo.rubyforge.org/">TZInfo - Ruby Timezone Library</a>
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compiles <code>tz</code> source into
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<a href="http://ruby-lang.org">Ruby</a>.
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It is freely available under the <abbr
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title="Massachusetts Institute of Technology">MIT</abbr> license.</li>
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<li>The <a href="http://chronos-st.org/">Chronos Date/Time
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Library</a> is a <a href="http://smalltalk.org">Smalltalk</a> class
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library that compiles <code>tz</code> source into a <a
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href="http://date-time-zone.com/">time zone repository</a> whose format
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is either proprietary or an <a href="http://www.w3.org/XML/"><abbr
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title="Extensible Markup Language">XML</abbr></a>-encoded
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representation.</li>
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<li>Starting with version 8.5, <a href="http://tcl.tk/">Tcl</a>
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contains a developer-oriented parser that compiles <samp>tz</samp>
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source into text files, along with a runtime that can read those
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files. Tcl is freely available under a <abbr>BSD</abbr>-style
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license.</li>
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</ul>
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<h2>Other <code>tz</code> binary file readers</h2>
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<ul>
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<li>The <a
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href="http://www.gnu.org/software/libc/"><abbr>GNU</abbr> C
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Library</a>
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has an independent, thread-safe implementation of
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a <code>tz</code> binary file reader.
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This library is freely available under the
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<a href="http://www.gnu.org/copyleft/lesser.html">
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<abbr>GNU</abbr> Lesser General Public License
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(<abbr title="Lesser General Public License">LGPL</abbr>)</a>,
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and is widely used in <abbr>GNU</abbr>/Linux systems.</li>
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<li><a href="http://bmsi.com/java/#TZ">ZoneInfo.java</a>
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is a <code>tz</code> binary file reader written in Java.
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It is freely available under the <abbr>LGPL</abbr>.</li>
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<li>Tcl, mentioned above, also contains a
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<code>tz</code> binary file reader.</li>
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</ul>
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<h2>Other <code>tz</code>-based time zone software</h2>
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<ul>
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<li><a href="http://stemhaus.com/firefox/foxclocks/">FoxClocks</a>
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is an extension for <a
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href="http://developer.mozilla.org/en/docs/Toolkit_API">Mozilla
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Toolkit</a> applications like <a
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href="http://mozilla.com/firefox">Firefox</a>, <a
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href="http://mozilla.com/thunderbird">Thunderbird</a>, and
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<a
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href="http://www.mozilla.org/projects/calendar/sunbird/">Sunbird</a>.
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It displays multiple clocks in the application window, and has a mapping
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interface to <a href="http://earth.google.com/">Google Earth</a>.
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It is freely available under the <abbr>GPL</abbr>.</li>
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<li><a
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href="http://users.skynet.be/Peter.Verthez/projects/intclock/">International
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clock (intclock)</a> is a multi-timezone clock for
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<abbr>GNU</abbr>/Linux and similar systems. It is freely available
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under the <abbr>GPL</abbr>.</li>
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<li><a href="http://codeplex.com/publicdomain">PublicDomain</a>
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|
|
has a copy of a recent <code>tz</code> database, accessed via a <a
|
||
|
|
href="http://en.wikipedia.org/wiki/C_Sharp">C#</a> library. As its
|
||
|
|
name suggests, it is in the public domain. Only current time stamps
|
||
|
|
are well supported; historical data are compiled into the runtime but
|
||
|
|
are not easily accessible.</li>
|
||
|
|
<li><a href="http://java.sun.com/">Sun Java</a> releases since 1.4
|
||
|
|
contain a copy of a subset of a recent <code>tz</code> database in a
|
||
|
|
Java-specific format.</li>
|
||
|
|
<li><a href="http://kimmo.suominen.com/sw/timezone/">Time Zone</a> is
|
||
|
|
a <a href="http://wordpress.org/">WordPress</a> plugin. It is freely
|
||
|
|
available under a <abbr>BSD</abbr>-style license.</li>
|
||
|
|
<li><a
|
||
|
|
href="http://veladg.com/velaterra.html">VelaTerra</a> is
|
||
|
|
a Mac OS X program. Its developers
|
||
|
|
<a href="http://veladg.com/tzoffer.html">offer free
|
||
|
|
licenses</a> to <code>tz</code> contributors.</li>
|
||
|
|
<li><a
|
||
|
|
href="http://worldtimeexplorer.com/">World Time Explorer</a> is a
|
||
|
|
Microsoft Windows program.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Other time zone databases</h2>
|
||
|
|
<ul>
|
||
|
|
<li><a href="http://www.astro.com/cgi/aq.cgi">Atlas Query</a>
|
||
|
|
is Astrodienst's Web version of Shanks's
|
||
|
|
excellent time zone history atlases published in both <a
|
||
|
|
href="http://astrocom.com/products/software.php?software_id=ibmwboth">computer</a>
|
||
|
|
and book form (<a
|
||
|
|
href="http://astrocom.com/products/book.php?book_id=b110x">one volume
|
||
|
|
for the USA</a>, and <a
|
||
|
|
href="http://astrocom.com/products/book.php?book_id=b112x">one for
|
||
|
|
other locations</a>) by <a
|
||
|
|
href="http://astrocom.com/">Astro Communications Services</a>.</li>
|
||
|
|
<li><a href="http://worldtime.com/">WORLDTIME: interactive atlas,
|
||
|
|
time info, public holidays</a>
|
||
|
|
contains information on local time, sunrise and sunset,
|
||
|
|
and public holidays in several hundred cities around the world.</li>
|
||
|
|
<li><a href="http://worldtimeserver.com/">World Time Server</a>
|
||
|
|
is another time zone database.</li>
|
||
|
|
<li><a href="http://tycho.usno.navy.mil/tzones.html">World Time Zones</a>
|
||
|
|
contains data from the Time Service Department of the
|
||
|
|
<abbr>US</abbr> Naval Observatory, used as the source
|
||
|
|
for the <code>usno*</code> files in the <code>tz</code> distribution.</li>
|
||
|
|
<li>The <a href="http://iata.org/ps/publications/SSIM.htm">Standard
|
||
|
|
Schedules Information Manual</a> of the
|
||
|
|
<a href="http://iata.org/index.htm">International Air Transport
|
||
|
|
Association</a>
|
||
|
|
gives current time zone rules for airports served by commercial aviation.</li>
|
||
|
|
<li>Some Microsoft Windows versions contain time zone information in
|
||
|
|
an undocumented format, with IDs that can be mapped to <code>TZ</code>
|
||
|
|
values using the <a
|
||
|
|
href="http://unicode.org/cldr/data/diff/supplemental/windows_tzid.html">Windows
|
||
|
|
→ Tzid table</a> maintained by the <abbr
|
||
|
|
title="Common Locale Data Repository">CLDR</abbr> data mentioned
|
||
|
|
below.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Maps</h2>
|
||
|
|
<ul>
|
||
|
|
<li>The <a href="https://www.cia.gov/">United States Central
|
||
|
|
Intelligence Agency (<abbr
|
||
|
|
title="Central Intelligence Agency">CIA</abbr>)</a> publishes a <a
|
||
|
|
href="https://www.cia.gov/library/publications/the-world-factbook/reference_maps/pdf/time_zones.pdf">time
|
||
|
|
zone map</a>; the
|
||
|
|
<a
|
||
|
|
href="http://www.lib.utexas.edu/maps/world.html">Perry-Castañeda
|
||
|
|
Library Map Collection</a>
|
||
|
|
of the University of Texas at Austin has copies of
|
||
|
|
recent editions.
|
||
|
|
The pictorial quality is good,
|
||
|
|
but the maps do not indicate summer time,
|
||
|
|
and parts of the data are a few years out of date.</li>
|
||
|
|
<li><a href="http://worldtimezone.com/">Current time around the world
|
||
|
|
and standard time zones map of the world</a>
|
||
|
|
has several fancy time zone maps; it covers Russia particularly well.
|
||
|
|
The maps' pictorial quality is not quite as good as the
|
||
|
|
<abbr>CIA</abbr>'s
|
||
|
|
but the maps are more up to date.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Time zone boundaries</h2>
|
||
|
|
<ul>
|
||
|
|
<li><a href="http://efele.net/maps/tz/">TZ timezone maps</a> contains a <a
|
||
|
|
href="http://en.wikipedia.org/wiki/Shapefile">shapefile</a> of the
|
||
|
|
<code>tz</code> regions in the world.</li>
|
||
|
|
<li><a href="http://statoids.com/statoids.html">Administrative Divisions
|
||
|
|
of Countries ("Statoids")</a> contains detailed lists of
|
||
|
|
<code>tz</code>-related zone subdivision data.</li>
|
||
|
|
<li><a href="http://home.tiscali.nl/~t876506/Multizones.html">Time
|
||
|
|
zone boundaries for multizone countries</a> summarizes legal
|
||
|
|
boundaries between time zones within countries.</li>
|
||
|
|
<li>Manifold.net's <a
|
||
|
|
href="http://www.manifold.net/download/freemaps.html">Free Maps and
|
||
|
|
<abbr title="Geographic Information Systems">GIS</abbr>
|
||
|
|
Data</a> includes a Manifold-format map of
|
||
|
|
world time zone boundaries distributed under the
|
||
|
|
<abbr>GPL</abbr>.</li>
|
||
|
|
<li>The <abbr>US</abbr> Geological Survey's National Atlas of
|
||
|
|
the United States
|
||
|
|
publishes the <a href="http://nationalatlas.gov/mld/timeznp.html">Time
|
||
|
|
Zones of the United States</a> in the public domain.</li>
|
||
|
|
<li>The GeoCommunity lists several commercial sources for <a
|
||
|
|
href="http://spatialnews.geocomm.com/features/timezones/">International
|
||
|
|
Time Zones and Time Zone Data</a>.</li>
|
||
|
|
<li>A ship within the <a
|
||
|
|
href="http://en.wikipedia.org/wiki/Territorial_waters">territorial
|
||
|
|
waters</a> of any nation uses that nation's time. In international
|
||
|
|
waters, time zone boundaries are meridians 15° apart, except that
|
||
|
|
UTC−12 and UTC+12 are each 7.5° wide and are separated by
|
||
|
|
the 180° meridian (not by the International Date Line, which is
|
||
|
|
for land and territorial waters only). A captain can change ship's
|
||
|
|
clocks any time after entering a new time zone; midnight changes are
|
||
|
|
common.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Civil time concepts and history</h2>
|
||
|
|
<ul>
|
||
|
|
<li><a href="http://physics.nist.gov/GenInt/Time/time.html">A
|
||
|
|
Walk through Time</a>
|
||
|
|
surveys the evolution of timekeeping.</li>
|
||
|
|
<li><a href="http://webexhibits.org/daylightsaving/">About Daylight
|
||
|
|
Saving Time - History, rationale, laws & dates</a>
|
||
|
|
is an overall history of <abbr>DST</abbr>.</li>
|
||
|
|
<li><a href="http://energy.ca.gov/daylightsaving.html">Saving Time,
|
||
|
|
Saving Energy</a> discusses a primary justification for <abbr>DST</abbr>.</li>
|
||
|
|
<li><a href="http://seizethedaylight.com/dst/">Who Knew? A Brief
|
||
|
|
History of Daylight Saving Time</a> summarizes some of the contentious
|
||
|
|
history of <abbr>DST</abbr>.</li>
|
||
|
|
<li><a href="http://toi.iriti.cnr.it/">The
|
||
|
|
Time of Internet</a>
|
||
|
|
describes time zones and daylight saving time,
|
||
|
|
with diagrams.
|
||
|
|
The time zone map is out of date, however.</li>
|
||
|
|
<li><a href="http://www.phys.uu.nl/~vgent/idl/idl.htm">A History of
|
||
|
|
the International Date Line</a> tells the story of the most important
|
||
|
|
time zone boundary.</li>
|
||
|
|
<li><a href="http://statoids.com/tconcept.html">Basic Time
|
||
|
|
Zone Concepts</a> discusses terminological issues behind time zones.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>National histories of legal time</h2>
|
||
|
|
<dl>
|
||
|
|
<dt>Australia</dt>
|
||
|
|
<dd>The Parliamentary Library has commissioned <a
|
||
|
|
href="http://www.aph.gov.au/LIBRARY/Pubs/rn/2006-07/07rn13.pdf">research
|
||
|
|
note on daylight saving time in Australia</a>.
|
||
|
|
The Bureau of Meteorology publishes a list of
|
||
|
|
<a href="http://www.bom.gov.au/climate/averages/tables/dst_times.shtml">Implementation Dates of Daylight Savings Time within Australia</a>.</dd>
|
||
|
|
<dt>Belgium</dt>
|
||
|
|
<dd>The Royal Observatory of Belgium maintains a table of <a
|
||
|
|
href="http://www.astro.oma.be/GENERAL/INFO/nli001a.html"
|
||
|
|
hreflang="nl">time in Belgium (in Dutch)</a>.</dd>
|
||
|
|
<dt>Brazil</dt>
|
||
|
|
<dd>The Time Service Department of the National Observatory
|
||
|
|
records <a href="http://pcdsh01.on.br/DecHV.html"
|
||
|
|
hreflang="pt-BR">Brazil's daylight saving time decrees (in
|
||
|
|
Portuguese)</a>.</dd>
|
||
|
|
<dt>Canada</dt>
|
||
|
|
<dd>The Institute for National Measurement Standards publishes current
|
||
|
|
and some older information about <a
|
||
|
|
href="http://inms-ienm.nrc-cnrc.gc.ca/time_services/daylight_saving_e.html">Time
|
||
|
|
Zones & Daylight Saving Time</a>.</dd>
|
||
|
|
<dt>Chile</dt>
|
||
|
|
<dd>The Chilean Hydrographic and Oceanographic Service publishes a <a
|
||
|
|
href="http://www.horaoficial.cl/horaof.htm" hreflang="es"> history of
|
||
|
|
official time (in Spanish)</a>.</dd>
|
||
|
|
<dt>Germany</dt>
|
||
|
|
<dd>The National Institute for Science and Technology maintains the <a
|
||
|
|
href="http://www.ptb.de/en/org/4/44/441/dars_e.htm">Realisation of
|
||
|
|
Legal Time in Germany</a>.</dd>
|
||
|
|
<dt>Israel</dt>
|
||
|
|
<dd>The Interior Ministry periodically issues <a
|
||
|
|
href="ftp://ftp.cs.huji.ac.il/pub/tz/announcements"
|
||
|
|
hreflang="he">announcements (in Hebrew)</a>.</dd>
|
||
|
|
<dt>Mexico</dt>
|
||
|
|
<dd>The Investigation and Analysis Service of the Mexican Library of
|
||
|
|
Congress has published a <a
|
||
|
|
href="http://www.cddhcu.gob.mx/bibliot/publica/inveyana/polisoc/horver/"
|
||
|
|
hreflang="es">history of Mexican local time (in Spanish)</a>.</dd>
|
||
|
|
<dt>Malaysia</dt>
|
||
|
|
<dd>See Singapore below.</dd>
|
||
|
|
<dt>Netherlands</dt>
|
||
|
|
<dd><a href="http://www.phys.uu.nl/~vgent/wettijd/wettijd.htm"
|
||
|
|
hreflang="nl">Legal time in the Netherlands (in Dutch)</a>
|
||
|
|
covers the history of local time in the Netherlands from ancient times.</dd>
|
||
|
|
<dt>New Zealand</dt>
|
||
|
|
<dd>The Department of Internal Affairs maintains a brief history <a
|
||
|
|
href="http://dia.govt.nz/diawebsite.nsf/wpg_URL/Resource-material-Information-We-Provide-About-Daylight-Saving">About
|
||
|
|
Daylight Saving</a>. The privately-maintained <a
|
||
|
|
href="http://astrologyschool.com/nztime.html">History of New Zealand
|
||
|
|
time</a> has more details.</dd>
|
||
|
|
<dt>Norway</dt>
|
||
|
|
<dd>The Norwegian Meteorological Institute lists
|
||
|
|
<a href="http://met.no/met/met_lex/q_u/sommertid.html" hreflang="no">Summer
|
||
|
|
time in Norway (in Norwegian)</a>, citing the
|
||
|
|
Institute of Theoretical Astrophysics, Oslo.</dd>
|
||
|
|
<dt>Singapore</dt>
|
||
|
|
<dd><a
|
||
|
|
href="http://www.math.nus.edu.sg/aslaksen/teaching/timezone.html">Why
|
||
|
|
is Singapore in the "Wrong" Time Zone?</a> details the
|
||
|
|
history of legal time in Singapore and Malaysia.</dd>
|
||
|
|
<dt>United Kingdom</dt>
|
||
|
|
<dd><a
|
||
|
|
href="http://www.srcf.ucam.org/~jsm28/british-time/">History of
|
||
|
|
legal time in Britain</a> discusses in detail the country
|
||
|
|
with perhaps the best-documented history of clock adjustments.
|
||
|
|
The National Physical Laboratory also maintains an <a
|
||
|
|
href="http://www.npl.co.uk/server.php?show=ConWebDoc.2714">Archive
|
||
|
|
of Summer time dates</a>.</dd>
|
||
|
|
</dl>
|
||
|
|
<h2>Precision timekeeping</h2>
|
||
|
|
<ul>
|
||
|
|
<li><a
|
||
|
|
href="http://literature.agilent.com/litweb/pdf/5965-7984E.pdf">The
|
||
|
|
Science of Timekeeping</a> is a thorough introduction
|
||
|
|
to the theory and practice of precision timekeeping.</li>
|
||
|
|
<li><a href="http://www.ntp.org/"><abbr
|
||
|
|
title="Network Time Protocol">NTP</abbr>: The Network
|
||
|
|
Time Protocol</a>
|
||
|
|
discusses how to synchronize clocks of
|
||
|
|
Internet hosts.</li>
|
||
|
|
<li><a
|
||
|
|
href="ftp://ftp.rfc-editor.org/in-notes/rfc4833.txt">Timezone
|
||
|
|
Options for <abbr title="Dynamic Host Configuration Protocol">DHCP</abbr></a>
|
||
|
|
(Internet <abbr>RFC</abbr> 4833)
|
||
|
|
specifies a <a
|
||
|
|
href="http://www.dhcp.org/">DHCP</a> option for a server to configure
|
||
|
|
a client's time zone and daylight saving settings automatically.</li>
|
||
|
|
<li><a href="http://gauss.gge.unb.ca/GMT.UT.and.the.RGO.html">A Few
|
||
|
|
Facts Concerning <abbr title="Greenwich Mean Time">GMT</abbr>, <abbr
|
||
|
|
title="Universal Time">UT</abbr>, and
|
||
|
|
the <abbr title="Royal Greenwich Observatory">RGO</abbr></a>
|
||
|
|
answers questions like "What is the
|
||
|
|
difference between <abbr>GMT</abbr> and <abbr>UTC</abbr>?"</li>
|
||
|
|
<li><a
|
||
|
|
href="http://www.cv.nrao.edu/~rfisher/Ephemerides/times.html">Astronomical
|
||
|
|
Times</a> explains more abstruse astronomical time scales like
|
||
|
|
<abbr title="Terrestrial Dynamic Time">TDT</abbr>,
|
||
|
|
<abbr title="Geocentric Coordinate Time">TCG</abbr>, and
|
||
|
|
<abbr title="Barycentric Dynamic Time">TDB</abbr>.
|
||
|
|
<a href="http://www.ucolick.org/~sla/leapsecs/timescales.html">Time
|
||
|
|
Scales</a> goes into more detail, particularly for historical variants.</li>
|
||
|
|
<li>The <a href="http://iau.org/"><abbr
|
||
|
|
title="International Astronomical Union">IAU</abbr></a>'s <a
|
||
|
|
href="http://www.iau-sofa.rl.ac.uk/"><abbr
|
||
|
|
title="Standards Of Fundamental Astronomy">SOFA</abbr></a>
|
||
|
|
initiative publishes Fortran
|
||
|
|
code for converting among time scales like
|
||
|
|
<abbr title="International Atomic Time">TAI</abbr>,
|
||
|
|
<abbr>TDB</abbr>, <abbr>TDT</abbr> and
|
||
|
|
<abbr>UTC</abbr>.</li>
|
||
|
|
<li><a href="http://jpl.nasa.gov/basics/bsf2-3.htm">Basics of
|
||
|
|
Space Flight - Reference Systems - Time Conventions</a>
|
||
|
|
briefly explains interplanetary space flight timekeeping.</li>
|
||
|
|
<li><a
|
||
|
|
href="http://www.giss.nasa.gov/tools/mars24/help/notes.html">Technical
|
||
|
|
Notes on Mars Solar Time as Adopted by the Mars24 Sunclock</a> briefly
|
||
|
|
describes Mars Coordinated Time (<abbr
|
||
|
|
title="Mars Coordinated Time">MTC</abbr>) and the
|
||
|
|
diverse local time
|
||
|
|
scales used by each landed mission on Mars.</li>
|
||
|
|
<li><a href="http://leapsecond.com/">LeapSecond.com</a> is
|
||
|
|
dedicated not only to leap seconds but to precise time and frequency
|
||
|
|
in general. It covers the state of the art in amateur timekeeping, and
|
||
|
|
how the art has progressed over the past few decades.</li>
|
||
|
|
<li><a
|
||
|
|
href="http://hpiers.obspm.fr/eop-pc/products/bulletins/bulletins.html">Bulletins
|
||
|
|
maintained by the
|
||
|
|
<abbr title="International Earth Rotation Service">IERS</abbr>
|
||
|
|
<abbr title="Earth Orientation Parameters">EOP</abbr>
|
||
|
|
(<abbr title="Product Center">PC</abbr>)</a> contains official publications of
|
||
|
|
the Earth Orientation Parameters Product Center of the
|
||
|
|
International Earth Rotation Service, the committee that decides
|
||
|
|
when leap seconds occur.</li>
|
||
|
|
<li>The <a
|
||
|
|
href="http://six.pairlist.net/mailman/listinfo/leapsecs">Leap
|
||
|
|
Second Discussion List</a> covers <a
|
||
|
|
href="http://gauss.gge.unb.ca/papers.pdf/gpsworld.november99.pdf">McCarthy
|
||
|
|
and Klepczynski's proposal to discontinue leap seconds</a>,
|
||
|
|
discussed further in
|
||
|
|
<a href="http://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf">The
|
||
|
|
leap second: its history and possible future</a>.
|
||
|
|
The (now disbanded) <a href="http://members.aas.org/comms/leap.cfm"><abbr
|
||
|
|
title="American Astronomical Society">AAS</abbr> Leap Second
|
||
|
|
Committee</a> has solicited input on this proposal.
|
||
|
|
<a href="http://www.ucolick.org/~sla/leapsecs/">The
|
||
|
|
Future of Leap Seconds</a> covers this
|
||
|
|
contentious issue.</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Time notation</h2>
|
||
|
|
<ul>
|
||
|
|
<li>
|
||
|
|
<a href="http://www.cl.cam.ac.uk/~mgk25/iso-time.html">A Summary of
|
||
|
|
the International Standard Date and Time Notation</a> is a good
|
||
|
|
summary of
|
||
|
|
<a
|
||
|
|
href="http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=40874"><abbr
|
||
|
|
title="International Organization for Standardization">ISO</abbr>
|
||
|
|
8601:2004 -- Data elements and interchange formats -- Information
|
||
|
|
interchange -- Representation of dates and times</a>.</li>
|
||
|
|
<li>
|
||
|
|
<a href="http://www.w3.org/TR/xmlschema-2/#dateTime"><abbr>XML</abbr>
|
||
|
|
Schema: Datatypes - dateTime</a> specifies a format inspired by
|
||
|
|
<abbr>ISO</abbr> 8601 that is in common use in XML data.</li>
|
||
|
|
<li>
|
||
|
|
<a href="ftp://ftp.rfc-editor.org/in-notes/rfc2822.txt">Internet
|
||
|
|
Message Format</a> (Internet <abbr>RFC</abbr> 2822) §3.3
|
||
|
|
specifies the time notation used in email and <a
|
||
|
|
href="ftp://ftp.rfc-editor.org/in-notes/rfc2616.txt"><abbr>HTTP</abbr></a>
|
||
|
|
headers.</li>
|
||
|
|
<li>
|
||
|
|
<a href="ftp://ftp.rfc-editor.org/in-notes/rfc3339.txt">Date and Time
|
||
|
|
on the Internet: Timestamps</a> (Internet <abbr>RFC</abbr> 3339)
|
||
|
|
specifies an <abbr>ISO</abbr> 8601
|
||
|
|
profile for use in new Internet
|
||
|
|
protocols.</li>
|
||
|
|
<li>
|
||
|
|
<a href="http://www.hackcraft.net/web/datetime/">Date & Time
|
||
|
|
Formats on the Web</a> surveys web- and Internet-oriented date and time
|
||
|
|
formats.</li>
|
||
|
|
<li>
|
||
|
|
<a href="http://exit109.com/~ghealton/y2k/yrexamples.html">The
|
||
|
|
Best of Dates, the Worst of Dates</a> covers many problems encountered
|
||
|
|
by software developers when handling dates and time stamps.</li>
|
||
|
|
<li>The <a
|
||
|
|
href="http://unicode.org/cldr/">Unicode Common Locale Data Repository
|
||
|
|
(<abbr>CLDR</abbr>) Project</a> has localizations for time zone names,
|
||
|
|
abbreviations, identifiers, and formats. For example, it contains
|
||
|
|
French translations for "Eastern European Summer Time", "<abbr
|
||
|
|
title="Eastern European Summer Time">EEST</abbr>", and
|
||
|
|
"Bucharest". <a
|
||
|
|
href="http://unicode.org/cldr/data/charts/by_type/names.metazone.html">By-Type
|
||
|
|
Chart: names.metazone</a> shows these values for many locales.
|
||
|
|
<abbr>ICU</abbr> contains a mechanism for using this data.</li>
|
||
|
|
<li>Alphabetic time zone abbreviations should not be used as unique
|
||
|
|
identifiers for <abbr>UTC</abbr> offsets as they are ambiguous in
|
||
|
|
practice. For example, "<abbr>EST</abbr>" denotes 5 hours behind
|
||
|
|
<abbr>UTC</abbr> in English-speaking North America, but it denotes 10
|
||
|
|
or 11 hours ahead of <abbr>UTC</abbr> in Australia; and
|
||
|
|
French-speaking North Americans prefer
|
||
|
|
"<abbr title="Heure Normale de l'Est">HNE</abbr>" to
|
||
|
|
"<abbr>EST</abbr>". For <abbr>POSIX</abbr> the <code>tz</code>
|
||
|
|
database contains English abbreviations for all time stamps but in
|
||
|
|
many cases these are merely inventions of the database
|
||
|
|
maintainers.</li>
|
||
|
|
<li>Numeric time zone abbreviations typically count hours east of
|
||
|
|
<abbr>UTC</abbr>, e.g., <code>+09</code> for Japan and
|
||
|
|
<code>-10</code> for Hawaii. However, the <abbr>POSIX</abbr>
|
||
|
|
<code>TZ</code> environment variable uses the opposite convention. For
|
||
|
|
example, one might use <code>TZ="JST-9"</code> and
|
||
|
|
<code>TZ="HST10"</code> for Japan and Hawaii, respectively. If the
|
||
|
|
<code>tz</code> database is available, it is usually better to use
|
||
|
|
settings like <code>TZ="Asia/Tokyo"</code> and
|
||
|
|
<code>TZ="Pacific/Honolulu"</code> instead, as this should avoid
|
||
|
|
confusion, handle old time stamps better, and insulate you better from
|
||
|
|
any future changes to the rules. One should never set
|
||
|
|
<abbr>POSIX</abbr> <code>TZ</code> to a value like
|
||
|
|
<code>"GMT-9"</code>, though, since this would falsely claim that
|
||
|
|
local time is nine hours ahead of <abbr>UTC</abbr> and the time zone
|
||
|
|
is called "<abbr>GMT</abbr>".</li>
|
||
|
|
</ul>
|
||
|
|
<h2>Related indexes</h2>
|
||
|
|
<ul>
|
||
|
|
<li><a href="tz-art.htm">Time and the Arts</a></li>
|
||
|
|
<li><a href="http://www.dmoz.org/Reference/Time/">Open Directory -
|
||
|
|
Reference: Time</a></li>
|
||
|
|
<li><a href="http://directory.google.com/Top/Reference/Time/">Google Directory
|
||
|
|
- Reference > Time</a></li>
|
||
|
|
<li><a href="http://dir.yahoo.com/Science/Measurements_and_Units/Time">Yahoo!
|
||
|
|
Directory > Science > Measurements and Units > Time</a></li>
|
||
|
|
</ul>
|
||
|
|
</body>
|
||
|
|
</html>
|