On Thu, Aug 27, 2015 at 3:21 PM, Tim Peters tim.peters@gmail.com wrote:

(1) mktime is a neither cheap nor reliable (in all cases) way to compute is_dst; and,

Moreover, there are cases where it is not even possible to tell whether DST is in effect or not. For example, when Moscow switched from permanent summer time to permanent winter time last year and Russia revised its entire map of 7 time zones they did not tell anyone what the new value of tm_isdst should be.

Taking my favorite example of 1990 Kiev, Ukraine.

Running on Linux:

$ zdump -v -c 1992 Europe/Kiev| grep 1990 Europe/Kiev Sat Jun 30 22:59:59 1990 UTC = Sun Jul 1 01:59:59 1990 MSK isdst=0 gmtoff=10800 Europe/Kiev Sat Jun 30 23:00:00 1990 UTC = Sun Jul 1 01:00:00 1990 EET isdst=0 gmtoff=7200

Running on a Mac:

$ zdump -v Europe/Kiev| grep 1990 Europe/Kiev Sat Mar 24 22:59:59 1990 UTC = Sun Mar 25 01:59:59 1990 MSK isdst=0 Europe/Kiev Sat Mar 24 23:00:00 1990 UTC = Sun Mar 25 03:00:00 1990 MSD isdst=1 Europe/Kiev Sat Jun 30 21:59:59 1990 UTC = Sun Jul 1 01:59:59 1990 MSD isdst=1 Europe/Kiev Sat Jun 30 22:00:00 1990 UTC = Sun Jul 1 01:00:00 1990 EEST isdst=1

From either of the output above, can you tell me what color was the bear?