Left over from when you'd stay up too late when you had school the next day, but applied to adult life; For example going clubbing when you have work the next day
Andy: Ah man I had a massive hangover this morning, was nearly late for work!
James: Clubbing on a schoolnight? Tut tut!
James: Clubbing on a schoolnight? Tut tut!
by Calamity James August 21, 2009