There are 336 sleeps (336 days) until September 17 (Friday, September 17, 2027).
There are 336 days until September 17 (Friday, September 17, 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 17. Sleeps are the same as days.
336 sleeps is 48 weeks.