I'm (finally) upgrading from MT 2.661 to 3.3. In the manual, it says to be sure that no one is using the software during the upgrade process.

How do I do that? What if someone comments while the upgrade occurs?

I would think you would probably have to take the site off-line to do that. Which means a night-time maintenance/upgrade, most likely.

I can't think of any other way to ensure that NOBODY is viewing comments, posting comments, checking a trackback, etc., other than taking the site offline.

Will part of the maintenance include fixing the time/ timezone? It's currently GMT -7.5, based on the timestamp of what I just posted...

And, last I checked, you lived in GMT -5.0 (which always confused me, that you never changed the timezone from CA to FL time when you moved out of Kali)

Typically such error is to ensure a transaction is not lost. In this case, I wouldn't consider it critical that someone's comment is lost during the update. They may notify you of an error, but they can simply resubmit the comment at a later time. If you start noticing anonymous posting, upgrade then...

Turn off execute permission on the directory in which the MT scripts reside.