In DSA you have the option 'TIME SYNCHRONIZATION' in the 'Fault & Performance' tab (left on the screen).
Click on it and shedule it (like 1x month). The PBX will then be adjusted to the PC time. You need to keep DSA running (if you want to do it overnight).
Be aware that you have to do it for all 3 systems.
This option will take care of time zone differences.
Normally, the time of the CMS will follow the time of the switch, so that problem is solved at the same time.
Hope this helps,
Erik.