From: "Antti Kurenniemi" 

"Geo."  wrote in message
news:45eb334f$1{at}w3.nls.net...
>> No but calculations. Say you have a plane that leaves place X today at 9
>> PM, and the flight takes 3 and a half hours. Now if the flight happens at
>> the date when DST is applied, then it can mean the difference wether the
>> plane arrives at the same night or the next day. None of this is anything
>> special, but typically you use the OS provided functions for calculations
>> with time and date. Now the point here is that if the OS provided
>> functions do not match with reality, you may end up with incorrect
>> results (plane arrival date is wrong).
>
> Doesn't windows do all calculations in UTC? I thought everything was UTC
> and  only display was converted using the timezone?

Calculations are usually done behind the scenes in seconds or milliseconds
from a fixed epoch (to increase date by one, add XXX seconds to the current
time). The problem comes when you ask the system what date is second
120973240348 - with a bit of bad luck that number falls in the place where
the new DST rules differ from the old, and you get an incorrect result.


Antti Kurenniemi

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