The dates are stored in the db as UTC which is equivalent to GMT.
They are displayed based on the preferred time zone of the user viewing the page. However to correctly calculate the difference so that we can translate the GMT time to your time zone, we must also know what time zone the server is in. GreenwichMeantimeOffset should be the difference between server local time and GMT. If the viewing user is logged in (i.e you logged in as admin) then the display is adjusted to your preferred time zone from your user profile.
In the case of anonymous users (not on this page since we are talking about an admin page, but in other places like the blog) Dates are adjusted to the PreferredGreenwichMeantimeOffset setting. This way if I'm living in CST time zone but my server is on the west coast in PST, I can still make the default display adjust to CST so that my site reflects my time zone.
The server should adjust to energy savings but there is a limitation in the current implementation in that we don't have any handling for cases where the user is in different time zones during different times of the year. In that case, the user will have to adjust his preferred time zone when this happens.
Joe