There are 340 sleeps (340 days) until September 28 (Tuesday, September 28, 2027).
There are 340 days until September 28 (Tuesday, September 28, 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 28. Sleeps are the same as days.
340 sleeps is 48 weeks and 4 sleeps.