Máy tính giấc ngủ
The detailed guide below is currently available in English.
Why sleep cycles matter
Sleep moves through light, deep, and REM stages in cycles that average about 90 minutes. Waking mid-cycle — especially out of deep sleep — leaves you groggy even after plenty of rest, a phenomenon called sleep inertia. Counting backward from your alarm to land the wake-up between cycles is the simple idea behind every bedtime on this list.
Using the options
Aim for the latest bedtime that still gives you enough sleep — most adults need four to six cycles. If you cannot fall asleep quickly, the 15-minute buffer may be under- or over-estimating for you: adjust the latency field to match your own drift-off time, and give yourself a wind-down period before the recommended clock time.
Câu hỏi thường gặp
Are sleep cycles exactly 90 minutes?
No — 90 minutes is a useful average, but individual cycles run roughly 80–110 minutes and get longer toward morning. Treat the schedule as a target, not a precision instrument.
Why is one bedtime listed for the night before?
When your wake time is early, subtracting six or more hours crosses midnight. The label reminds you that bedtime belongs to the previous calendar day.