Time Zone Settings

Does anyone know where Windows stores it’s Time Zone Settings? I’ve got 108 pcs and my predecessor didn’t seem to know what time zone he lived in (GMT -5:00) and quite a few of the pcs are set in different time zones. I was hoping there was a registry key I could change (RPC or scripts) but I was not able to find any differences using Windiff to compare a registry after a time zone change. Any ideas? Thanks.