The real informal understanding IMHO was that rules should be there for a sensible reason. The reason for giving a 4pm deadline usually is that you want to grad

The real informal understanding IMHO was that rules should be there for a sensible reason. The reason for giving a 4pm deadline usually is that you want to grade the submissions sometime after 4pm. The reason for giving a midnight deadline is that it is a deadline and you've got to give deadlines.