There is no clock in PhotoPost. I mean in a standalone install a user can edit there timeoffset in there profile and we show the server time so the user can select there correct timezone offset.
I know I have explained in full details here about GMT etc so without more info it is hard to say what your exact settings would be.
If your using vb
or invisionboard the time offset comes from the users forum profile and you use GMT to bring your server time back to GMT time which means say a server in central time which is -7 from GMT you would put 7 in the GMT setting then your time should be synced with vb
Now that is the only time you use GMT setting in PhotoPost when integrated with those two products otherwise all other products use timezone offsets from the server time like out product.