Daylight Savings Time in Local Timezones

nbagley

I am trying to determine the local daylight savings times for all timezones around the world. I am basing my date and time on GMT (although I don't have to), and I get local times right now, but the problem that I am having I have no way (or no clue right now) how to get when a users local timezone DST has started or stoped. I was thinking of setting up a SQL database to house all of the dates where DST starts and stop in each area (...a pain the butt if you ask me), but I was wondering is there a way that I can dynamically test each timezone (northern and southern hemisphere) to see if they are on DST or not? Any formula to do the trick? Any suggestions would be a great help. Thanks.

roger20

Good luck, you'll need it!

There's no algorithm that you can code into your application since DST is done at government level (on a vote around a table).

Do a few searches on Google with "daylight saving algorithm" or whatever, and pages like this crop up http://www.timeanddate.com

I supose it can be done for major locations but you'll need to keep checking for governments fiddling with things.

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Roger

nbagley

Thanks for the infomation. I had a feeling that was going to be the case. Do you know how other companies deal with DST in their online applications that deal with users around the world? If they simply ignore this then I think that I can stop worring about my project. Either that, or I have some work and maintanace to do... oh well, that is the life of a programmer... Thanks again.

Nathan

roger20

Do a search at Google Groups (newsgroup search) on "daylight saving algorithm" and you'll pick up a few pointers from people using languages other than php. It's a universal problem!

Forums like this just let you manually adjust the time to make it display at whatever happens to be your localtime. More time critical applications often need something to handle questions like "what was the local time in country X at GMT 01/01/1999 12:30" Problem eh?

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Roger

nbagley

Yep. That is my problem. My program (which is a web site tracker) is very time oriented, and if I don't get it right for each timezone, I think that a few people will be unhappy that their web site is tracking hits that are supposed to be at 3pm and at it records it at 5pm. Hmm, I'll figure it out. Thanks for all your help, I will have to see what magic I can work... Nathan