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diff --git a/unused/tz-link.htm b/unused/tz-link.htm new file mode 100644 index 000000000000..0cd9e28a3056 --- /dev/null +++ b/unused/tz-link.htm @@ -0,0 +1,648 @@ +<!DOCTYPE html + PUBLIC "-//W3C//DTD HTML 4.01//EN" + "http://www.w3.org/TR/html4/strict.dtd"> +<html> +<head> +<title>Sources for Time Zone and Daylight Saving Time Data</title> +<link rel="schema.DC" href="http://purl.org/DC/elements/1.1/"> +<meta http-equiv="Content-type" content='text/html; charset="US-ASCII"'> +<meta name="DC.Creator" content="Eggert, Paul"> +<meta name="DC.Contributor" content="Olson, Arthur David"> +<meta name="DC.Date" content="2007-12-26"> +<meta name="DC.Description" + content="Sources of information about time zones and daylight saving time"> +<meta name="DC.Identifier" content="http://www.twinsun.com/tz/tz-link.htm"> +<meta name="Keywords" + content="database,daylight saving,DST,time zone,timezone,tz,zoneinfo"> +</head> +<body> +<h1>Sources for Time Zone and Daylight Saving Time Data</h1> +<address> +@(#)tz-link.htm 8.18 +</address> +<p> +Please send corrections to this web page to the +<a href="mailto:tz@elsie.nci.nih.gov">time zone mailing list</a>.</p> +<h2>The <code>tz</code> database</h2> +<p> +The <a href="http://en.wikipedia.org/wiki/Public_domain">public-domain</a> +time zone database contains code and data +that represent the history of local time +for many representative locations around the globe. +It is updated periodically to reflect changes made by political bodies +to <a href="http://en.wikipedia.org/wiki/Time_zone">time zone</a> +boundaries, <a +href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time"><abbr +title="Coordinated Universal Time">UTC</abbr></a> offsets, and +<a href="http://en.wikipedia.org/wiki/Daylight_saving">daylight-saving</a> +rules. +This database (often called <code>tz</code> or <a +href="http://en.wikipedia.org/wiki/Zoneinfo"><code>zoneinfo</code></a>) +is used by several implementations, +including +<a href="http://www.gnu.org/software/libc/">the +<abbr title="GNU's Not Unix">GNU</abbr> +C Library</a> used in +<a href="http://www.linux.org/"><abbr>GNU</abbr>/Linux</a>, +<a href="http://www.freebsd.org/">FreeBSD</a>, +<a href="http://netbsd.org/">NetBSD</a>, +<a href="http://openbsd.org/">OpenBSD</a>, +<a href="http://cygwin.com/">Cygwin</a>, +<a href="http://www.delorie.com/djgpp/"><abbr +title="DJ's GNU Programming Platform">DJGPP</abbr></a>, +<a href="http://ibm.com/aix">AIX</a>, +<a href="http://www.apple.com/macosx/">Mac OS X</a>, +<a href="http://h71000.www7.hp.com/">OpenVMS</a>, +<a href="http://oracle.com/database">Oracle Database</a>, +<a href="http://sun.com/software/solaris">Solaris</a>, +<a href="http://h30097.www3.hp.com/">Tru64</a>, and +<a href="http://sco.com/products/unixware">UnixWare</a>.</p> +<p> +Each location in the database represents a national region where all +clocks keeping local time have agreed since 1970. +Locations are identified by continent or ocean and then by the name of +the location, which is typically the largest city within the region. +For example, <code>America/New_York</code> +represents most of the <abbr title="United States">US</abbr> eastern time zone; +<code>America/Phoenix</code> represents most of Arizona, which +uses mountain time without daylight saving time (<abbr +title="daylight saving time">DST</abbr>); +<code>America/Detroit</code> represents most of Michigan, which uses +eastern time but with different <abbr>DST</abbr> rules in 1975; +and other entries represent smaller regions like Starke County, +Indiana, which switched from central to eastern time in 1991 +and switched back in 2006. +To use the database on an extended <a +href="http://en.wikipedia.org/wiki/POSIX"><abbr +title="Portable Operating System Interface">POSIX</abbr></a> +implementation set the <code>TZ</code> environment variable to +the location's full name, e.g., <code>TZ="America/New_York"</code>.</p> +<p> +In the <code>tz</code> database's +<a href="ftp://elsie.nci.nih.gov/pub"><abbr +title="File Transfer Protocol">FTP</abbr> distribution</a> +the code is in the file <code>tzcode<var>C</var>.tar.gz</code>, +where <code><var>C</var></code> is the code's version; +similarly, the data are in <code>tzdata<var>D</var>.tar.gz</code>, +where <code><var>D</var></code> is the data's version. +The following <a +href="http://en.wikipedia.org/wiki/Unix_shell">shell</a> commands download +these files to a <abbr>GNU</abbr>/Linux or similar host; +see the downloaded +<code>README</code> file for what to do next.</p> +<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' +<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 - +gzip -dc tzdata*.tar.gz | tar -xf - +</code></pre> +<p> +The code lets you compile the <code>tz</code> source files into +machine-readable binary files, one for each location. It also lets +you read a <code>tz</code> binary file and interpret time stamps for that +location.</p> +<p> +The data are by no means authoritative. If you find errors, please +send changes to the <a href="mailto:tz@elsie.nci.nih.gov">time zone +mailing list</a>. You can also <a +href="http://news.gmane.org/gmane.comp.time.tz">browse recent +messages</a> sent to the mailing list, <a +href="mailto:tz-request@elsie.nci.nih.gov">subscribe</a> to it, +retrieve the <a +href="ftp://elsie.nci.nih.gov/pub/tzarchive.gz">full archive of old +messages</a> (in gzip compressed format), or retrieve <a +href="ftp://munnari.oz.au/pub/oldtz">archived older versions of code +and data</a>; there is also a smaller <a +href="http://public.planetmirror.com/pub/timezone"><abbr +title="Hypertext Transfer Protocol">HTTP</abbr> +mirror</a>.</p> +<p> +The Web has several other sources for time zone and daylight saving time data. +Here are some recent links that may be of interest. +</p> +<h2>Web pages using recent versions of the <code>tz</code> database</h2> +<p> +These are listed roughly in ascending order of complexity and fanciness. +</p> +<ul> +<li><a href="http://twiki.org/cgi-bin/xtra/tzdatepick.html">Date and Time Gateway</a> +lets you see the <code>TZ</code> values directly.</li> +<li><a +href="http://convertit.com/Go/ConvertIt/World_Time/Current_Time.ASP">Current +Time in 1000 Places</a> uses descriptions of the values.</li> +<li><a href="http://www.timezoneconverter.com/">Time Zone Converter</a> +uses a pulldown menu.</li> +<li><a href="http://home.tiscali.nl/~t876506/TZworld.html">Complete +timezone information for all countries</a> displays tables of DST rules. +<li><a href="http://timeanddate.com/worldclock/">The World Clock - +Time Zones</a> lets you sort zone names and convert times.</li> +<li><a href="http://daylight-savings-time.info/">Graphical Display of +Time Zones and Daylight Saving Times</a> shows a graph of time +difference versus time for any pair of locations.</li> +<li>The <a href="http://worldtimeengine.com/">World Time Engine</a> +also contains data about time zone boundaries; it supports queries via place +names and shows location maps.</li> +</ul> +<h2>Other time zone database formats</h2> +<ul> +<li>The <a href="ftp://ftp.rfc-editor.org/in-notes/rfc2445.txt"> +Internet Calendaring and Scheduling Core Object Specification +(iCalendar)</a>, Internet <abbr title="Request For +Comments">RFC</abbr> 2445, published by the (now-concluded) <a +href="http://ietf.org/html.charters/OLD/calsch-charter.html"><abbr +title="Internet Engineering Task Force">IETF</abbr> +Calendaring and Scheduling Working Group (<abbr +title="Calendaring and Scheduling Working Group">calsch</abbr>)</a> +covers time zone +data; see its VTIMEZONE calendar component. +The <a href="http://calconnect.org/">Calendaring and Scheduling +Consortium</a> is promoting further work in this area. <a +href="http://calconnect.org/publications/icalendartimezoneproblemsandrecommendationsv1.0.pdf">iCalendar +TIMEZONE Problems and Recommendations</a> offers guidelines and +recommendations for the use of VTIMEZONE and <code>tz</code>.</li> +<li><a href="http://calconnect.org/dstlinks.shtml">Extended Daylight +Saving Time Links, Advisories and Changes</a> lists vendor material on recent +daylight saving time changes.</li> +<li><a +href="http://calconnect.org/publications/timezoneregistryandservicerecommendationsv1.0.pdf">Timezone +Registry and Service Recommendations</a> discusses a +strategy for defining and deploying a time zone +registration process that would establish unique names for each +version of each <code>tz</code> zone, along with a polygonal +representation of the geographical area corresponding to the +zone.</li> +<li>The <a +href="http://lists.w3.org/Archives/Public/www-rdf-calendar/">www-rdf-calendar</a> +list discusses <a +href="http://www.w3.org/RDF/"><abbr +title="Resource Description Framework">RDF</abbr></a>-based calendar +and group scheduling systems, and has a <a +href="http://www.w3.org/2002/12/cal/#tzd">workspace on time zone +data</a> converted from <code>tz</code>. An earlier <a +href="http://www.w3.org/2000/01/foo">schema</a> was sketched out.</li> +</ul> +<h2>Other <code>tz</code> compilers</h2> +<ul> +<li><a href="http://www.dachaplin.dsl.pipex.com/vzic/">Vzic iCalendar +Timezone Converter</a> describes a <a +href="http://en.wikipedia.org/wiki/C_%28programming_language%29">C</a> +program that compiles +<code>tz</code> source into iCalendar-compatible VTIMEZONE files. +Vzic is freely +available under the <a +href="http://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr> +General Public License (<abbr +title="General Public License">GPL</abbr>)</a>.</li> +<li><a href="http://sourceforge.net/projects/tzical">tziCal - tz +database conversion utility</a> is like Vzic, except for the <a +href="http://msdn.microsoft.com/netframework">.NET framework</a>.</li> +<li><a +href="http://search.cpan.org/dist/DateTime-TimeZone/">DateTime::TimeZone</a> +contains a script <code>parse_olson</code> that compiles +<code>tz</code> source into <a href="http://www.perl.org/">Perl</a> +modules. It is part of the Perl <a +href="http://datetime.perl.org/">DateTime Project</a>, which is freely +available under both the <abbr>GPL</abbr> and the Perl Artistic +License. DateTime::TimeZone also contains a script +<code>tests_from_zdump</code> that generates test cases for each clock +transition in the <code>tz</code> database.</li> +<li><a href="http://icu-project.org/">International Components for +Unicode (<abbr>ICU</abbr>)</a> contains C/C++ and <a +href="http://en.wikipedia.org/wiki/Java_%28programming_language%29">Java</a> +libraries for internationalization that +has a compiler from <code>tz</code> source +into an <abbr>ICU</abbr>-specific format. +<abbr>ICU</abbr> is freely available under a +<abbr title="Berkeley Software Distribution">BSD</abbr>-style license.</li> +<li><a href="http://joda-time.sourceforge.net/">Joda Time - Java date +and time <abbr title="Application Program Interface">API</abbr></a> +contains a class +<code>org.joda.time.tz.ZoneInfoCompiler</code> that compiles +<code>tz</code> source into a Joda-specific binary format. Joda Time +is freely available under a <abbr>BSD</abbr>-style license.</li> +<li><a href="http://pytz.sourceforge.net">PyTZ - Python Time +Zone Library</a> compiles <code>tz</code> source into +<a href="http://python.org/">Python</a>. +It is freely available under a <abbr>BSD</abbr>-style license.</li> +<li><a href="http://tzinfo.rubyforge.org/">TZInfo - Ruby Timezone Library</a> +compiles <code>tz</code> source into +<a href="http://ruby-lang.org">Ruby</a>. +It is freely available under the <abbr +title="Massachusetts Institute of Technology">MIT</abbr> license.</li> +<li>The <a href="http://chronos-st.org/">Chronos Date/Time +Library</a> is a <a href="http://smalltalk.org">Smalltalk</a> class +library that compiles <code>tz</code> source into a <a +href="http://date-time-zone.com/">time zone repository</a> whose format +is either proprietary or an <a href="http://www.w3.org/XML/"><abbr +title="Extensible Markup Language">XML</abbr></a>-encoded +representation.</li> +<li>Starting with version 8.5, <a href="http://tcl.tk/">Tcl</a> +contains a developer-oriented parser that compiles <samp>tz</samp> +source into text files, along with a runtime that can read those +files. Tcl is freely available under a <abbr>BSD</abbr>-style +license.</li> +</ul> +<h2>Other <code>tz</code> binary file readers</h2> +<ul> +<li>The <a +href="http://www.gnu.org/software/libc/"><abbr>GNU</abbr> C +Library</a> +has an independent, thread-safe implementation of +a <code>tz</code> binary file reader. +This library is freely available under the +<a href="http://www.gnu.org/copyleft/lesser.html"> +<abbr>GNU</abbr> Lesser General Public License +(<abbr title="Lesser General Public License">LGPL</abbr>)</a>, +and is widely used in <abbr>GNU</abbr>/Linux systems.</li> +<li><a href="http://bmsi.com/java/#TZ">ZoneInfo.java</a> +is a <code>tz</code> binary file reader written in Java. +It is freely available under the <abbr>LGPL</abbr>.</li> +<li>Tcl, mentioned above, also contains a +<code>tz</code> binary file reader.</li> +</ul> +<h2>Other <code>tz</code>-based time zone software</h2> +<ul> +<li><a href="http://stemhaus.com/firefox/foxclocks/">FoxClocks</a> +is an extension for <a +href="http://developer.mozilla.org/en/docs/Toolkit_API">Mozilla +Toolkit</a> applications like <a +href="http://mozilla.com/firefox">Firefox</a>, <a +href="http://mozilla.com/thunderbird">Thunderbird</a>, and +<a +href="http://www.mozilla.org/projects/calendar/sunbird/">Sunbird</a>. +It displays multiple clocks in the application window, and has a mapping +interface to <a href="http://earth.google.com/">Google Earth</a>. +It is freely available under the <abbr>GPL</abbr>.</li> +<li><a +href="http://users.skynet.be/Peter.Verthez/projects/intclock/">International +clock (intclock)</a> is a multi-timezone clock for +<abbr>GNU</abbr>/Linux and similar systems. It is freely available +under the <abbr>GPL</abbr>.</li> +<li><a href="http://codeplex.com/publicdomain">PublicDomain</a> +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/us/">A map of the TZ timezones in +the US</a> contains a <a +href="http://en.wikipedia.org/wiki/Shapefile">shapefile</a> of the +<code>tz</code> regions in the US.</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> |