There are 220 sleeps (220 days) until May 31 (Monday, May 31, 2027).
There are 220 days until May 31 (Monday, May 31, 2027) — one sleep per night.
One sleep per night between now and the big day — tonight is the first sleep, and the morning after the last sleep is May 31. Sleeps are the same as days.
220 sleeps is 31 weeks and 3 sleeps.