There are 90 sleeps (90 days) until January 21 (Thursday, January 21, 2027).
There are 90 days until January 21 (Thursday, January 21, 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 January 21. Sleeps are the same as days.
90 sleeps is 12 weeks and 6 sleeps.