From: Trevor Squires Date: 2006-02-02T07:36:18+09:00 Subject: Re: Time zone offset and daylight saving Hi, Regarding "good luck figuring out when you're supposed to switch" - Phil Ross has released a ruby library that uses the Olson Timezone database (considered the definitive source for world timezones). You're right that it's a pain (it's a political issue after all) but it's not insurmountable if you use the Olson data. Phil's library is available at: http://tzinfo.rubyforge.org/ HTH, Trevor On 1-Feb-06, at 1:38 PM, JM wrote: > My understanding is that a time change is implemented by switching > time > zones; you change from Pacific Standard Time to Pacific Daylight Time. > Pacific Standard Time would continue to have the same offset in > July as it > would in January; it's just that in July no clocks are set to Pacific > Standard. (Except the clock on my kitchen scale, of course...) > > And good luck figuring out when you're supposed to switch; it's > arbitary, > set by legislation, not by something you can figure out. And the > US at > least will be changing in the near future. And there are places > that never > make the switch, too. Google for things like 'daylight savings > time zone' > and you'll get an idea of the pain involved. > > - James > > wrote in message > news:1138565845.900427.111410@g14g2000cwa.googlegroups.com... >> I don't seem to be able to correctly calculate the time offset >> between >> two time zones when daylight saving is in effect. The code below >> demonstrates that Ruby knows about daylight saving, but I get the >> wrong >> answer when I calculate the offset. >> >> BTW, yes, I know I can use Time#utc_offset, but I believe that >> depends >> on me actually being in that timezone. I'm looking for a way to >> calculate the offset between two arbitrary timezones, neither of >> which >> is my local timezone. >> >> Thanks for any help. >> >> David > > -- Trevor Squires http://somethinglearned.com