“Even a stopped clock gives the right time twice a day”. 
SDMB server’s clock reflects Chicago local time, not GMT. The server’s clock is set correctly.
The
The labels in the drop-down box (on User Control Panel > Edit Options > Time offset:) are incorrect 6 months of the year. That’s why there’s a FAQ post explaining it. The labels are not automatically modified when the server clock changed. That’s not my decision (I am not a vBulletin developer).
The point is, that what the Board calls “GMT” is (almost) always the time in England, but the time in England is not always GMT. Of course, even if that were fixed, there’s still the brief discontinuity from England and the U. S. not switching at the same time, but that’s relatively minor.
And while the British Isles may not see as much temperature variation as does the U. S., they see more variation in the length of the day than we do, so if anything, it makes more sense for the Isles to go to some sort of “summer time”.