2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
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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
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href="http://en.wikipedia.org/wiki/C_Sharp">C#</a> library. As its
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name suggests, it is in the public domain. Only current time stamps
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are well supported; historical data are compiled into the runtime but
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are not easily accessible.</li>
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<li><a href="http://java.sun.com/">Sun Java</a> releases since 1.4
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contain a copy of a subset of a recent <code>tz</code> database in a
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Java-specific format.</li>
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<li><a href="http://kimmo.suominen.com/sw/timezone/">Time Zone</a> is
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a <a href="http://wordpress.org/">WordPress</a> plugin. It is freely
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available under a <abbr>BSD</abbr>-style license.</li>
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<li><a
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href="http://veladg.com/velaterra.html">VelaTerra</a> is
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a Mac OS X program. Its developers
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<a href="http://veladg.com/tzoffer.html">offer free
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licenses</a> to <code>tz</code> contributors.</li>
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<li><a
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href="http://worldtimeexplorer.com/">World Time Explorer</a> is a
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Microsoft Windows program.</li>
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</ul>
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<h2>Other time zone databases</h2>
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<ul>
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<li><a href="http://www.astro.com/cgi/aq.cgi">Atlas Query</a>
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is Astrodienst's Web version of Shanks's
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excellent time zone history atlases published in both <a
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href="http://astrocom.com/products/software.php?software_id=ibmwboth">computer</a>
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and book form (<a
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href="http://astrocom.com/products/book.php?book_id=b110x">one volume
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for the USA</a>, and <a
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href="http://astrocom.com/products/book.php?book_id=b112x">one for
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other locations</a>) by <a
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href="http://astrocom.com/">Astro Communications Services</a>.</li>
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<li><a href="http://worldtime.com/">WORLDTIME: interactive atlas,
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time info, public holidays</a>
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contains information on local time, sunrise and sunset,
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and public holidays in several hundred cities around the world.</li>
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<li><a href="http://worldtimeserver.com/">World Time Server</a>
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is another time zone database.</li>
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<li><a href="http://tycho.usno.navy.mil/tzones.html">World Time Zones</a>
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contains data from the Time Service Department of the
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<abbr>US</abbr> Naval Observatory, used as the source
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for the <code>usno*</code> files in the <code>tz</code> distribution.</li>
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<li>The <a href="http://iata.org/ps/publications/SSIM.htm">Standard
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Schedules Information Manual</a> of the
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<a href="http://iata.org/index.htm">International Air Transport
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Association</a>
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gives current time zone rules for airports served by commercial aviation.</li>
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<li>Some Microsoft Windows versions contain time zone information in
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an undocumented format, with IDs that can be mapped to <code>TZ</code>
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values using the <a
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href="http://unicode.org/cldr/data/diff/supplemental/windows_tzid.html">Windows
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→ Tzid table</a> maintained by the <abbr
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title="Common Locale Data Repository">CLDR</abbr> data mentioned
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below.</li>
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</ul>
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<h2>Maps</h2>
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<ul>
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<li>The <a href="https://www.cia.gov/">United States Central
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Intelligence Agency (<abbr
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title="Central Intelligence Agency">CIA</abbr>)</a> publishes a <a
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href="https://www.cia.gov/library/publications/the-world-factbook/reference_maps/pdf/time_zones.pdf">time
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zone map</a>; the
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<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>
|