Forum time is UTC+1
To get the accurate time do I set Time Offset: -1?
If that is correct then we should be seeing same posting time with the time here.
Can anyone correct me that I got the right time offset?
Yes, that's correct. You have now set your time to UTC. If that's what you are trying to set.
If you just want to sync with forum's time just use 0 in the time offset box.
Edit: now I get you're trying to set the forum's time so as I said previously just type 0 instead of -1.