If I said "the servers are down for maintenance at 2am tomorrow" when would you think they will be unavailable?
If you said "2am tomorrow" I would assume two hours after next midnight. Perhaps this is a result of my usually late schedule because I normally go to bed around 2am, so everything up to then and including midnight is "tonight".
If I said "the servers are down for maintenance at 2am tomorrow" when would you think they will be unavailable?