My computer clock’s in sync pretty much with the 11 o’clock news’s, and the SDMB says it’s actually 3 minutes ahead. I’ve noticed that the time around here is sometimes the same as my computer’s, sometimes it’s ahead, and sometimes it’s behind. Why is it so screwed up?
I would guess because the server for the SDMB is very accurate and your computer is off; or both of them are off; or yours is accurate and the server is off because it’s not “synched” to an atomic clock.
A man with one clock always knows exactly what time it is. A man with two clocks is never sure.
I don’t remember where I read this, but it applies here.
There is another possibility which occurs when I visit. After reaching the forums page I click on the forum I wish to read. If, having read the messages, I then use the back button to return to the front page, the time displayed is the time when I first arrived at the site. If however I return to the front page via one of the links at the top of the page ( because I have posted, for example) then the time displayed is the current time.
Yikes. I just checked the SDMB clock against the USNO clock. We’re between 2m50s and 3m00s fast. Good thing I never use this clock. 
During peak usage periods, vital hamster power is sometimes diverted from the SDMB clock in order to keep up with the demand for “Page Not Found” errors.