What time should I go to bed if I wake up at 5:45 pm?

Waking at 5:45 pm is a night-shift schedule: sleep runs through the day, with lights out at 10:00 am for five cycles or 8:30 am for six.

Why three times and not one

The middle option, 10:00 am, is five cycles and 7 h 30 min of actual sleep; 8:30 am is six cycles and 9 h. Both sit inside the adult range. The 11:30 am option is 6 h: enough to get through the day, not enough to do it twice.

Sleep moves from light sleep into deep sleep and then REM, and one pass takes about 90 minutes — anywhere from 70 to 120 depending on the person and the point in the night. That spread is why these are windows, not appointments.

In clock terms: lights out 10:00 am, asleep around 10:15 am, deepest sleep of the night between roughly 10:35 am and 11:45 am, the night's midpoint at 2:00 pm, and REM building toward 5:10 pm. The 5:45 pm alarm lands as cycle 5 closes, so you are likely in light sleep rather than deep.

All bedtimes for a 5:45 pm alarm

Formula: bedtime = wake time − (cycles × 90 min) − 15 min · adult range from the NSF 2015 panel and the AASM/SRS 2015 consensus · methodology

If you can't fall asleep by 10:00 am

Two things stretch the fifteen minutes most people need to drop off: caffeine within six hours of 10:00 am (that is 4:00 am), and a screen in the last hour. If neither applies and you are still awake twenty minutes in, get up for a while rather than lying there, and come back for the 11:30 am window.

Try a different time