By default, when non-privileged users connect to Windows XP desktops, they see the time zone of the system running the desktop instead of the time zone of their own user device. This does not apply to Windows Vista or Windows 7, which have a separate time zone privilege.
To allow Windows XP users to see their local time you need to give them rights to:
After you do this, users who connect to Windows XP desktops see their local time zone reflected in the desktop. When they log off or disconnect, the time zone of the desktop is reset to what it was before they logged on.
You can configure time zone settings through Citrix policies. Use the Use local time of client policy setting in the Time Zone Control section of the ICA Policy Settings folder.