Calculate time on base of TimeZone, Daylight saving

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I am searching for a ready made function which return time,
input will be time, Target time zone (for ex: EDT), flag to consider day light saving or not.

Input and result time can be in any format like CTime, SYSTEMTIME, etc.

Thanks.

Posted 24-Nov-10 17:53pm

Shaishav

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fjdiewornncalwe 25-Nov-10 13:59pm

What have you tried to do? What is the problem you encountered.

3 solutions

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Richard MacCutchan · Accepted Answer · 2010-12-10T03:24:00

Solution 2

You just need to set your time value into a struct tm
and use the localtime()[^] function. See also the Time Management[^] routines.

Posted 10-Dec-10 3:24am

Richard MacCutchan

T2102 · Accepted Answer · 2010-12-12T13:14:00

Solution 3

Don't use localtime. It does not work properly, especially if you are using time zones outside the US. You might try BOOST.

Posted 12-Dec-10 13:14pm

T2102

Andrew Phillips · Accepted Answer · 2010-12-10T01:18:00

This is what I think you are asking for:

INPUT 1: time in UTC ("Greenwich" time)
INPUT 2: time zone string (3 characters)
INPUT 3: bool to say whether DST is to be considered
OUTPUT: local time in that time zone at that time

This is a difficult problem. First you would have to restrict the range of input times. It would be hard to say whether DST was/will be in effect for dates a long time in the past or dates in the future.

There is no way using standard C/C++ functions to get this information. I don't even think you would be able to ask Windows if a certain day in the past used DST. (DST start and end times often vary from year to year). And if you can I wouldn't trust the answer.

I think you would have to research this yourself to build up a table of when DST started and ended for all the time zones you are interested in for the range of dates you want. You also need a table to convert the 3 character time zone codes to +/- hours from UTC time.

I doubt whether anyone has written a general function to do this, or even if all the information to do so has been gathered into the one place.

It may also be a problem that some input times can correspond to 2 different output times.