There are 325 sleeps (325 days) until September 13 (Monday, September 13, 2027).
There are 325 days until September 13 (Monday, September 13, 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 September 13. Sleeps are the same as days.
325 sleeps is 46 weeks and 3 sleeps.