Calculates the best times to fall asleep tonight.
Includes ~14 minutes to fall asleep. Calculates best wake-up times.
Why 90 minutes? A complete sleep cycle lasts approximately 90 minutes and includes light sleep, deep sleep, and REM. Waking mid-cycle — especially during deep sleep — causes grogginess. The average adult needs 5–6 complete cycles (7.5–9 hours). Waking at the end of a cycle feels significantly more refreshing.