At the end of the bank run scene from "It's a Wonderful Life", special significance is given to 6 PM. That is, Potter warns George, "If you close your doors before 6 PM you will never reopen!" Also, George et al at Building and Loan excitedly count down to 6 PM.
What is the reason for this? When George initially arrives at the B&L, Uncle Billy had already locked the doors. Other than not wanting to lose his customers' confidence, is there some particular necessity to be open until 6?