Thanks for the prompt answer CloudedVision.

Actually, I am already utilizing PHP to get the server side time and also, the REQUIRED time for the user based on the saved time difference data.

However, I can not use server side to determine what is the time on the user's PC, and actually this script would need to check if the server side data is accurate.

The challenge here: I could make a comparison of JAVA user time string and PHP server side string to see if it matches even without converting the user side time to a unix timestamp, BUT, here is an example where this fails:

user time string: 2008-Apr-12 14:59
server required string: 2008-Apr-12 15:01

I wanted a 3 minutes threshold that is acceptable as the difference between server side and user side, but in this case I can not calculate it without using timestamps since not even the hours match.

I could make EXCEPTIONS but that would take lots and lots of rows and resources.

That is why I asked this question if anyone knows a better solution for this trouble.