We recently launched a new Web presence for my German Church using Joomla 2.5. At my suggestion, GCalendar was installed to provide a searchable event calendar and an "upcoming events" module. It all worked splendidly until British Summertime began on 31 March 2013 - and suddenly all calendar events were shown starting an hour early.
We spent days trying to find a way to configure Daylight Savings into the calendar. All it allowed us to do in the global settings was to choose a time zone - of course we had set it to Europe/London - but without an option of respecting Daylight Savings automatically. In despair, I eventually uninstalled the component and reinstalled it. At this point there was a new version (3.0.0) of GCalendar available, so I chose that. In the component control panel there turned out to be an options button at the top right of the screen, which we may simply have missed seeing before. In the options you can set the time zone and once I had done so, suddenly all the times appeared correctly again within the web site. Huge sighs of relief all round.