Hardware Clock to GMT instead of local time

[Ali Onur UYAR]

I had been using Debian since July of 1998. It had been a dual boot
NT/Debian Box. At the time of installation I remember selecting
something like 'Set HW Clock to Local Time'. Now that I've dumped NT
completely and I want to change it to 'HW Clock set to GMT' as I believe
that is the way UNIXish machines should be configured.
The question is: what configuration, startup scripts am I supposed to
modify so that everthing will work correctly.