Tuesday

Nothing special, or in particular, without reason. Tuesday is a day in the week where nothing really happens and to which no particular meaning is tied. When someone does something bc it's a Tuesday, it means it doesn't really have a deeper meaning.

When asking why someone does something seemingly random, which they either do a lot or they themselves don't know why they're doing it;
"idk must be Tuesday"
"Because it's Tuesday I guess?"
"Well it's a Tuesday so..."
¯\_(ツ)_/¯