Somebody's got a case of the Mondays

Meaning

A condescending or playful way to point out that someone is in a foul mood at the start of the work week. It implies that the person is merely suffering from the universal struggle of returning to work rather than having a legitimate problem.

Sarcastic, patronizing

Used in a sentence

• You have been staring at your computer for an hour without typing a word. Looks like somebody has a case of the Mondays.
• Stop sighing every time the phone rings. Somebody has a case of the Mondays, don't they?
• I would offer you some coffee, but it looks like somebody has a case of the Mondays today.