There is a specific ending date to every auction, however a few things modify that time.

1. When the auctioneer lists the item, he chooses how long the auction will run.
2. When a bid is put in in the last few minutes of an auction, up to 5 minutes are added to the closing time of the auction to eliminate sniping at the last second.
3. The amount of seconds an auction has left are not listed. Since a last second bid adds a few minutes to the time, seconds are not necessary.
4. Other than that, the auction ends when the listed time is reached.