How to check when Daylight Saving Time (DST) will commence?

Using time zone dumper utility (zdump) like this:

zdump -v /etc/localtime | grep 2007

we can see that:

/etc/localtime Sun Mar 25 00:59:59 2007 UTC = Sun Mar 25 01:59:59 2007 CET isdst=0 gmtoff=3600
/etc/localtime Sun Mar 25 01:00:00 2007 UTC = Sun Mar 25 03:00:00 2007 CEST isdst=1 gmtoff=7200
/etc/localtime Sun Oct 28 00:59:59 2007 UTC = Sun Oct 28 02:59:59 2007 CEST isdst=1 gmtoff=7200
/etc/localtime Sun Oct 28 01:00:00 2007 UTC = Sun Oct 28 02:00:00 2007 CET isdst=0 gmtoff=3600

DST will commence on 25th of March and end on 28th of October. All days valid for year 2007 in the Central European Time (CET) timezone. Feel free to check start and end times for your local timezone.