Firstly, ensure that your server's clock is right. If it isn't, ask your sysadmin to set the server's clock right - synchronising to an internet NTP server is usually best.
The server's time zone is irrelevant and won't affect anything as long as it's right.
You can set the TZ environment variable to a known time zone, and have the PHP date/time functions change their behaviour accordingly. Try this in your shell, for example:
TZ='Europe/London' date
TZ='America/Los_Angeles' date
Setting $_ENV{'TZ'} will affect this in PHP.
You can get a list of all the time zones on Debian Linux by using the "tzselect" program.
Unfortunately I don't know whether this works on Windows - possibly not.
Mark
