I've noticed that since we switched to daylight savings time here recently, the timestamps are off by 1 hour for people living in the US. For instance, I am in US eastern standard time and the time here is currently 3:06pm, which is UTC-4:00. However, the forum reports it as UTC-5:00, or 2:06pm. For part of the year we are UTC-4:00, and for the other part we are UTC-5:00.
I think this has to do with different countries handling daylight savings time differently (this was unknown to me until recently). I realize this might be a bit tricky to fix in general because there's a lot of variation with how countries handle time.
Details:
http://en.wikipedia.org/wiki/Daylight_saving_time