For a client of ours I have a login script that runs commands to set the timezone. Most of our clients use Thin or Zero clients to connect to the VD's and never seem to pull the correct time zone for their location.
using ifmember to determine the groups the user belongs to I issue a tzutil command to set the time zone at logon. different groups get different timezones set based on membership
if you are simply wanting all desktops to stay on the Central Time zone you can issue a "tzutil /s "central standard time"" command in a login script and that will set the timezone to CST each time the users log in.
