On Thu, 2003-11-13 at 02:16, Simon Marlow wrote:
I think you're assuming that the timezone TLAs don't represent fixed offsets relative to UTC. I assume that they do.
For example, here we are in timezone GMT at the moment (== UTC+0000), but we switch to BST in the summer (UTC+0100).
I just looked up the list of timezone abbreviations, and it's pretty short. The library could easily include this list.
Where did you find this list? With a little Google searching I found several conflicting sources: http://www.weltzeituhr.com/laender/zeitzonen_e.shtml has MANY meanings for some TLA's: (AST could be Al Manamah, Anguilla, Antigua, Antilles, Arabia, Arabic, or Atlantic Standard Time; or Asia Time). Brazil is listed has having BRT for Brasilia Time (for the middle and east) or for Brasil Time (for the south) or BRST for the south "Summer Time". http://home-4.tiscali.nl/~t876506/Multizones.html lists for Brazil "Atlantic time", "Central Brazil time", "Amazone time", and "Acre time", with no mentioned abbreviations. http://www.mhonarc.org/MHonArc/doc/resources/timezones.html says that BST is British Summer, and that BZT2 is Brazil Zone 2 (no mention of other Brazil zones); but mentions at the bottom that BST may also be Brazil Standard. http://www.cryst.bbk.ac.uk/listproc/vsns-pps-technical/9501/0031.html lists information retrieved from SysVR4 timezone files; here, EST could mean Canada/Eastern or US/Eastern (-5:00), Brazil/East (-3:00), Chile/EasterIsland (-6:00), or Australia/Tasmania (+10:00). The data which is currently "authoritative", at least for Linux (the ultimate source for the files in my /usr/share/zoneinfo directory), is the tzdata package from ftp://elsie.nci.nih.gov/pub/. The latest version (as of this writing), tzdata2003d.tar.gz, is less ambiguous than the SysVR4 data, but still contains ambiguities (a quick check reveals EST for Australia (+10:00) and the US (-5:00); there's actually some discussion of the issue, in the file "australasia", which mentions IST: Israel Standard Time (+2:00), India Standard Time (+5:30), Irish Summer Time).
Perhaps we want a way to map geographical locations to timezones.
Ooh, dangerous. Microsoft took its cool timezone world map out of post-Windows 95 (I think) editions because of political issues: some territory was disputed between two countries, who wanted to apply different timezones to the territory; so Microsoft's map was seen as endorsing one country as the "correct" owner of the territory. (I don't remember the details.) Would you have, like tzdata does, a separate "time zone" for Boise, Idaho? Boise is in Mountain time; but, according to tzdata, it switched into or out of daylight savings time four weeks late in 1974 (I was there at the time, but I was only 5, so I don't remember), so it's listed separately (in case somebody wants to know what the local time would have been in 1974, I guess). I recommend reading through the files in tzdata for a LOT of interesting time zone anecdotes (things like "Shanks partitions Indiana into 345 regions, each with its own time history, and writes ``Even newspaper reports present contradictory information.''" and "I know one story of a town on one time zone having its school in another, such that a mom had to serve her family lunch in two shifts." Carl Witty