[tz] Regarding mktime issue

Paul Eggert eggert at cs.ucla.edu
Thu Mar 9 22:10:09 UTC 2017

On 03/09/2017 03:37 AM, Gopesh Kumar Chaudhary wrote:
> Is it expected behavior of mktime to give non DST epoch for both DST 
> and non DST time stamp ?

If you give mktime a valid struct tm whose tm_isdst value is positive 
and mktime returns successfully, the resulting tm_isdst should also be 
positive. Likewise for when tm_isdst is zero. The test case you 
supplied, however, had a negative tm_isdst, and this told mktime that 
you didn't know whether the timestamp used DST and that it was OK for 
mktime to assume either DST or non-DST.

In cases where multiple valid answers could be returned, the standard 
does not specify which answer is "correct". So GNU mktime is operating 
correctly here.

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