If your systems are set correctly they should be in the proper time zone. If you are running anything from 2K and up, they will sync with your DC's and adjust their time accordingly.
Make sure the local PC's are set for the correct time zones and get your DC's talking to an authoritative NTP server (at least a Stratum 2).
This should fix your problems and when users log in, their outlook reminders (assuming of course you are using outlook), will adjust to the current time zone.
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Today is the tomorrow you worried about yesterday.
