On Linux servers you'd often find a directory /usr/share/timezoneinfo which contains a buncha different timezones and DST rules. Creating a symbolic /etc/timezone to the appropriate one of these files will set the server's local time (assuming that the server's internal clock is calibrated to UTC).
For details, just found this
As for Windows servers, well... there's probably a copy of tzedit floating around on the install CD somewhere..
And never need to faff around with daylight saving again (or at least, not until the server moves to a different timezone, or the local Powers that Be redefine DST).
I don't remember - how do you expect me to remember something that happened three weeks ago?