Time zone settings using STZAC

Hello SAP Guru's,

I was looking for some suggestions/answers on a query I have.

In our 4.6C system, The OS level Time zone is in EDT, also when I check System > Status i can see the correct time as per OS level.

But in STZAC i can see it as CET (for both 'System time zone' & 'Default time zone')

Please let me know, what I can do to make it in sync. What time zone settings should be done in STZAC ? and will it have any adverse effect on users or system data ?

Regards,

Arpit Shroff