Originally Posted by clarence5ybr

"Saturday night stay" is an informal way of summarizing the actual fare rule. To my knowledge, DL doesn't have an actual fare rule that reads "Saturday night stay required".

An example of a DL minimum stay requirement is as follows (for a TE10Q3SJ fare basis):
MINIMUM STAY: RETURN FIRST SUNDAY AFTER DEPARTURE FROM ORIGIN

So DL's "miniumum stay" rules don't actually require that you stay anywhere, just that you don't fly back until a certain amount of time has elapsed after your departure.