Time limitations on auctions

[excaliber7388]

I'm making an auction house on my server that is ran entirely by one NPC. I know how to make everything for bidding and selling, however, the time limit is what's nailing me. I have an idea, but I have to know more first.
1st question-does timevar2 continue to increase, or does it stop at a certain number?
2nd is timevar2 exact seconds? Would lag throw it off?
Ex: would it be safe to say that timevar2+3600 is 1 hour from now?
Thanks!