2 pm is probably the cut off time. Meaning... they've switched over to the next banking day. So, for example, while it's Monday, after 2pm, it's Tuesday for the banks. Yes, cash is immidiate; you can take money out through the atm, you can purchases... but, if you have anything posting that night, and you made a deposit to cover what's supposed to post that night, the cash isn't going to cover it. Why? It's next business day. Technically, you made the deposit as if you were coming in Tuesday morning and making the deposit. So, it won't post until that time at midnight. What gets really tricky with that... if the debit/credit card merchants aren't on the same business day. That's the part that really screws you over. Some merchants don't cut over at the same time.
But, that in itself, is another story.