Home timezone can be now selected via profile page:

By default it's set to UTC for everyone. GMT based folks are better off selecting their actual time zone - e.g. Europe/London or Europe/Lisbon - so it will track the DST. Drop down shows current timezone offset from the UTC, so for London it will be 0:00 today, but it will be 1:00 from April to October.
When browsing calendar not logged in, timezone will default to UTC.