Sleeping Pills
Bob was having trouble getting to sleep at night. He went to see his doctor, who prescribed some extra-strong sleeping pills.
Sunday night Bob took the pills, slept well and was awake before he heard the alarm. He took his time getting to the office, strolled in and said to his boss: I didn't have a bit of trouble getting up this morning.
That's fine, roared the boss, but where were you Monday and Tuesday?