Wirelessly posted (8700g: BlackBerry8700/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)
Here are some tips, for what it's worth, partly repeating what has already been posted.
First, the BBFAQ, Why doesn't my time update correctly when I change Time Zones? - BlackBerryFAQ
Additionally, if you choose to use the time zone feature of the blackberry:
* Think of the start and end time as referenced to the time displayed by the blackberry and whatever time zone setting applied.
* When you create an entry in calendar or tasks, set the time and the time zone according to where the appointment or whatever occurs. If you are setting an event that crosses time zones, set the time zone based on the zone in which the start time occurs (i.e. flight boarding time) and set the duration of the event (i.e. flight time). When the entry is saved, the blackberry converts the times to the time zone setting on the blackberry.
* Your appointments and events in other time zones will be offset by the difference from the time zone setting on the blackberry, but your local (i.e. local is where you happen to be, and you have set the blackberry to the local time zone) appointments, etc. will show at correct local time when you change the zone setting to the local time zone wherever you are at that time. But regardless, the times will be referenced to the time on the blackberry. If you have a 10:00AM flight out of Atlanta and you set a calendar alert for 30 minutes before the flight, but your blackberry is still set to Pacific Time, your alert will still activate at 30 minutes before the flight.
* Be sure to return the setting to you home time zone before syncing with your home computer.