When you’re not sure when daylight saving time changes you can quickly check it using the zdump command which is available on every *nix system.
To check this year’s daylight saving time changes for Europe/Warsaw time zone execute command:
$ zdump -v Europe/Warsaw | grep 2012
Europe/Warsaw Sun Mar 25 00:59:59 2012 UTC = Sun Mar 25 01:59:59 2012 CET isdst=0 gmtoff=3600
Europe/Warsaw Sun Mar 25 01:00:00 2012 UTC = Sun Mar 25 03:00:00 2012 CEST isdst=1 gmtoff=7200
Europe/Warsaw Sun Oct 28 00:59:59 2012 UTC = Sun Oct 28 02:59:59 2012 CEST isdst=1 gmtoff=7200
Europe/Warsaw Sun Oct 28 01:00:00 2012 UTC = Sun Oct 28 02:00:00 2012 CET isdst=0 gmtoff=3600
As you can see for Europe/Warsaw time zone – the clock moves forward one hour to Central European Summer Time on 25 March 2012 (2:00 → 3.00 local time) and goes back one hour to Central European Time on 28 October 2012