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Corrections to latitudes/longitudes in zone.tab
by Andy McDonald May 22, 2006

May 22, 2006

Hi, A very very minor point, but I've run across a few inaccurate latitudes/longitudes in tz's zone.tab (2006g and earlier): Corrected lat/long zone.tab lat/long America/Argentina/Tucuman: -0265000, -0651300 -0312400, -0641100 America/Inuvik: +0682200, -1334400 +0682500, -1133000 America/Rainy_River: +0484300, -0943400 +0484300, -0942900 America/Rankin_Inlet +0624800, -0920500 +0624500, -0921000 America/Scoresbysund: +0703000, -0215800 +0703000, -0221500 (Tucuman's latitude and longitude in zone.tab are those of America/Argentina/Cordoba.) The corrected values come from playing with my Firefox extension (http://www.stemhaus.com/firefox/foxclocks/) and Google Earth, and are of course entirely subjective. Regards, Andy McDonald

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timezones offset from what?
by Zefram May 19, 2006

May 19, 2006

I've been doing work on precision timekeeping on computer systems. Naturally I don't use timezones at all inside that code, but there are places where I need to apply timezones when presenting a time to non-specialist humans. Looking through the zoneinfo database and the theory written about it, it struck me that although it deals fantastically with what time offset to use, there's no rigorous treatment of what base time scale to apply the offset to. Then it struck me that a simple treatment of this could solve a couple of other issues with the database. An example of this issue: as the zoneinfo source notes, UK legal time is currently based on mean solar time on the Greenwich meridian. Now that's not even Universal Time any more, since the prime meridian moved (slightly) off the Greenwich meridian. But everyone in the UK in practice sets their clocks based on UTC, as promulgated by the NPL and the BBC. At centisecond timescales, GMT (legal time in the UK), UTC (used in practice), UT1 (which UTC tracks in the long term), and UT2 (used for civil time in the 1950s) are all quite distinct. So I have a suggestion: it would be nice if the zoneinfo database included a field identifying exactly which time scale to apply the offsets to. The database doesn't need to understand how the time scales relate to each other; leave that to the precision horologists. All it needs is a short text string, with values such as "UTC", "UT1", "GMT". Of course, in a lot of cases this information is unavailable, or the distinction wasn't being made, so you'd then give "UT" to be explicitly ambiguous about the exact flavour of Universal Time. This field would also allow the database to handle timezones that are based on something other than UT. Currently the data files for Saudi Arabia attempt to describe apparent solar time in terms of UT, by means of a daily offset change. But it could instead be specified as a fixed offset with a base of apparent solar time on the prime meridian. To understand the zone properly the code would need to calculate the equation of time, but that only needs to be implemented once and it would give a much smoother and more accurate result than the daily UT offset changes do. A system that doesn't do the equation of time would effectively fall back to mean solar time, which is what the Riyadh8X zones do anyway. It's also a way to handle Mars time. Just specify the base to be MTC instead of UT. Ta da. What do you think? -zefram

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Correction
by Behdad Elahipanah May 17, 2006

May 17, 2006

Tehran's (Iran) current UTC/GMT Offset is: +3:30 hours with no daylight saving time at the moment Please correct it in your database.

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Kirov on GMT+4?
by Jesper Norgaard Welen May 16, 2006

May 16, 2006

The Kirov timezone according to the tz database is GMT+3. As you will remember in an earlier mail I could not find any mention of the timezone directly in the page of the Kirovskaya oblast' in http://www.gov-vyatka.ru/ however this page pointed to another page http://www.gismeteo.ru/weather/towns/27196.htm that has sunrise and sunset times indicating that Kirov is on GMT+3. Now I have found a page that points to this same page, but explicitly defines Kirov as being on GMT+4: >From main page http://map.rin.ru selecting Kirovskaya obl. http://map.rin.ru/cgi-bin/main.pl?Region=kirov you can see just below the link to the www.gismeteo.ru link that it specifies explicitly GMT+4 The other links confirm what we think for other oblast's in the area: Samarskaya oblast' on GMT+4: http://map.rin.ru/cgi-bin/main.pl?Region=samara Udmurtskaya oblast' on GMT+4: http://map.rin.ru/cgi-bin/main.pl?Region=udmurt Volgogradskaya oblast' on GMT+3: http://map.rin.ru/cgi-bin/main.pl?Region=volga Astrakhanskaya oblast' on GMT+3: http://map.rin.ru/cgi-bin/main.pl?Region=astrah Saratovskaya oblast' on GMT+3: http://map.rin.ru/cgi-bin/main.pl?Region=saratov Komi republic on GMT+3: http://map.rin.ru/cgi-bin/main.pl?Region=komi This page has a summary of time differences from Moscow time, and shows Kirov as being on Moscow time, e.g. GMT+3: http://www.bereg.ru/sprav_info/inform/time.shtml As we know from an earlier email from Paul Eggert, Shanks & Pottenger (2003) has Kirov on GMT+4. I'm afraid Kirov is a difficult case. I have changed it myself in World Time Explorer 4 times from between GMT+4 and GMT+3: February 23, 2000 GMT+4 to GMT+3 January 21, 2001 GMT+3 to GMT+4 June 18, 2001 GMT+4 to GMT+3 October 2, 2002 GMT+3 to GMT+4 Each time I was convinced I had found a better source. So who are we to believe? We have still not found any official russian page that gives the GMT offset explicitly. - Jesper Jesper Nørgaard Welen Email: jnorgard(a)Prodigy.Net.mx Project Leader (Líder de Proyecto) Software CIMMYT - Centro Internacional de Mejoramiento de Maíz y Trigo Dirección: CIMMYT Int. c/o Jesper Nørgaard Km. 45, Carretera México-Veracruz El Batán Texcoco, Edo. de México CP 56130 MEXICO Tel.: +52 (55) 58-04-20-04 ext. 1374 Fax: +52 (55) 58-04-75-58 Tel. Casa: 53-10-05-95 ó 53-10-97-78 Download the free program World Time Explorer, I made: http://www.worldtimeexplorer.com/index.html

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FW: Finnish summer time (DST) rule
by Olson, Arthur David (NIH/NCI) [E] May 15, 2006

May 15, 2006

Jukka A. Ukkonen is not on the time zone mailing list; direct replies appropriately. --ado -----Original Message----- From: Jukka A. Ukkonen [mailto:jau@iki.fi] Sent: Friday, May 12, 2006 1:57 AM To: tz(a)lecserver.nci.nih.gov Subject: Finnish summer time (DST) rule Greetings from Kirkkonummi (32km from Helsinki), The correct DST rule (in POSIX TZ syntax) for Finland has been at least since 2002 EET-02:00EEST-03:00,M3.5.0/03:00,M10.5.0/04:00 Notice that in there the zone change times are represented in the local time of the zone which is current at the moment when the change shall take place - i.e. both local times actually refer to 01:00 GMT. I guess Finland used this rule already several years before the common EU directive officially harmonized the DST rules all around EU from 2002 onwards. The EU directive can be found here... http://europa.eu.int/eur-lex/pri/en/oj/dat/2001/l_031/l_03120010202en002 10022.pdf I will let you know, if I find more precise info about when Finland actually adopted the current DST rule. Cheers, // jau .--- ..- -.- -.- .- .- .-.-.- ..- -.- -.- --- -. . -. / Jukka A. Ukkonen, Oxit Ltd, Finland /__ M.Sc. (sw-eng & cs) (Phone) +358-500-606-671 / Internet: Jukka.Ukkonen(a)Oxit.Fi (Home) +358-9-6215-280 / Internet: jau(a)iki.fi v .--- .- ..- ...-.- .. -.- .. .-.-.- ..-. .. + + + + My opinions are mine and mine alone, not my employers. + + + +

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Finnish summer time (DST) rule
by jau＠iki.fi May 11, 2006

May 11, 2006

Greetings from Kirkkonummi (32km from Helsinki), The correct DST rule (in POSIX TZ syntax) for Finland has been at least since 2002 EET-02:00EEST-03:00,M3.5.0/03:00,M10.5.0/04:00 Notice that in there the zone change times are represented in the local time of the zone which is current at the moment when the change shall take place - i.e. both local times actually refer to 01:00 GMT. I guess Finland used this rule already several years before the common EU directive officially harmonized the DST rules all around EU from 2002 onwards. The EU directive can be found here... http://europa.eu.int/eur-lex/pri/en/oj/dat/2001/l_031/l_03120010202en002100… I will let you know, if I find more precise info about when Finland actually adopted the current DST rule. Cheers, // jau .--- ..- -.- -.- .- .- .-.-.- ..- -.- -.- --- -. . -. / Jukka A. Ukkonen, Oxit Ltd, Finland /__ M.Sc. (sw-eng & cs) (Phone) +358-500-606-671 / Internet: Jukka.Ukkonen(a)Oxit.Fi (Home) +358-9-6215-280 / Internet: jau(a)iki.fi v .--- .- ..- ...-.- .. -.- .. .-.-.- ..-. .. + + + + My opinions are mine and mine alone, not my employers. + + + +

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Russia +4 breakout oblasts
by Jesper Norgaard Welen May 10, 2006

May 10, 2006

Oscar van Vlijmen made (as far as I understand) a thourough investigation of the Russian timezones in 2001-08-25 which documented all the oblasts that the russian timezones covers, listing the oblast's that correspond to each timezone. There are many english-speaking sites that to this day disagree with specific cities (stating that Kirov is on GMT+4 and similar), but after checking some russian sites I have come to the conclusion that the highly appreciated work of Oscar is still corresponding to current time in those places. However, all of the russian timezones in the tz database are declared as having been unaltered since 1991-1993 (this differs a bit from one russian timezone to the other), and especially the Europe/Samara timezone is unchanged since 1991 Oct 20 3:00. The following maps show the oblast' Kirovskaya, Saratovskaya, Volgogradskaya and Astrakhanskaya to be on GMT+4 as well: http://www.odci.gov/cia/publications/factbook/reference_maps/pdf/time_zones. pdf http://www.statoids.com/tru.html http://www.manifold.net/download/freemaps.html http://www.lib.utexas.edu/maps/world_maps/time_zone_world_98.jpg This is also true for a recent (1995+) ESRI map of timezones I have seen. The above links are all taken directly or indirectly from http://www.twinsun.com/tz/tz-link.htm Oscar is correct that since 2001 these were no longer on GMT+4 but had returned to GMT+3, but this return we have not documented with one or several timezones. I am not aware when these changes happened, but any guess would be better than the current state, where these four oblast' are on Moscow time since 1880, which is hardly likely to be true, if so many map makers have insisted on that they were on GMT+4 or even GMT+5. Regards, - Jesper Jesper Nørgaard Welen Email: jnorgard(a)Prodigy.Net.mx Project Leader (Líder de Proyecto) Software CIMMYT - Centro Internacional de Mejoramiento de Maíz y Trigo Dirección: CIMMYT Int. c/o Jesper Nørgaard Km. 45, Carretera México-Veracruz El Batán Texcoco, Edo. de México CP 56130 MEXICO Tel.: +52 (55) 58-04-20-04 ext. 1374 Fax: +52 (55) 58-04-75-58 Tel. Casa: 53-10-05-95 ó 53-10-97-78 Download the free program World Time Explorer, I made: http://www.worldtimeexplorer.com/index.html

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Bermuda will adopt US rules next year
by Paul Eggert May 7, 2006

May 7, 2006

In today's Royal Gazette, Stuart Roberts reports that Bermuda will fall into line with the US daylight-saving rules next year; see <http://www.theroyalgazette.com/apps/pbcs.dll/article?AID=/20060506/NEWS/105…>. Currently the tz tables take advantage of the fact that Bermuda and the Bahamas use the same DST rules, and have done so since 1974. My guess is that the Bahamas will fall into line as well, but I have no info about this, so perhaps it's better to play it safe for now and split these rules. There's no rush on this, since the new Bermuda rules don't affect time stamps until March 2007. Besides the Bahamas, other countries to watch on this front include Cuba, Haiti, Mexico, and Turks and Caicos.

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DST in Honduras, El Salvador, Guatemala, Nicaragua
by Jesper Norgaard Welen May 6, 2006

May 6, 2006

There is a flood of mutually conflicting stories on the near past/future DST changes in Honduras, El Salvador, Guatemala and Nicaragua. Here is a small bouquet of articles to consider, not that I will pretend to judge which are true or false: Change of DST in Honduras: http://ar.news.yahoo.com/060503/4/qmx7.html expected for this Sunday 7 at 0:00 Change of DST perhaps postponed in El Salvador: http://www.laprensagrafica.com/lodeldia/883.asp ... it has the interesting claim that Honduras changed the same time as Guatemala and Nicaragua. Change of DST in Guatemala: http://www.deguate.com/cgi-bin/noticias/print.pl?article=7134 claims that the return of DST will happen the 30.th. of September at 24 hours, or really 1.st. of October at 0:00. Another confirmation that Nicaragua change was at 2:00 in the morning: http://www.elnuevodiario.com.ni/2006/05/01/nacionales/18410: Por orden del presidente de la República, Enrique Bolaños, Nicaragua adelantó en sesenta minutos su hora oficial, ayer a las dos de la mañana, y así permanecerá hasta el 30 de septiembre. This means the following (my informal translation) By order of the president of the republic, Enrique Bolaños, Nicaragua advanced by sixty minutes their official time, yesterday at 2 in the morning, and will stay that way until 30.th. of september. Jesper Nørgaard Welen Email: jnorgard(a)Prodigy.Net.mx Project Leader (Líder de Proyecto) Software CIMMYT - Centro Internacional de Mejoramiento de Maíz y Trigo Dirección: CIMMYT Int. c/o Jesper Nørgaard Km. 45, Carretera México-Veracruz El Batán Texcoco, Edo. de México CP 56130 MEXICO Tel.: +52 (55) 58-04-20-04 ext. 1374 Fax: +52 (55) 58-04-75-58 Tel. Casa: 53-10-05-95 ó 53-10-97-78 Download the free program World Time Explorer, I made: http://www.worldtimeexplorer.com/index.html

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Honduras and El Salvador on DST too?
by Oscar van Vlijmen May 5, 2006

May 5, 2006

Reportedly (wordltimezone.com, some Spanish media) Honduras chose to follow Guatemala and will observe DST starting "la medianoche del sábado", so probably Saturday 06 May 2006, 24:00 local time. No ending date is mentioned other than "durante cuatro meses hasta septiembre" (during 4 months until September). My theory is: DST ends Saturday 02 September 2006 24:00 local time. El Salvador will follow Honduras. No serious details, no serious sources were given. I couldn't find any more reliable sources yet. Does anybody know more of this?

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