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Screen Curfew Calculator

Enter your bedtime and how long before bed you want to stop screens.

Result

23:35
00:20
45 min

How it is calculated

The bedtime is read as a 24-hour clock time (HH:MM) and converted to minutes after midnight: bed = hours × 60 + minutes. The cutoff window is rounded to a whole number of minutes, then subtracted: curfew = (bed − cutoff) mod 1440, where 1440 is the number of minutes in a day. The remainder is turned back into HH:MM, so a result earlier than midnight wraps onto the previous evening instead of going negative. A cutoff longer than a day also wraps around (1500 minutes lands on the same clock time as 60 minutes).

Only the time of day is computed; no dates are involved. Bedtime must be written as 24-hour HH:MM (09:05 or 9:05), and 12-hour entries such as 10:30 PM give no result. A negative cutoff also gives no result.

Worked example

Your bedtime is 00:20 (twenty past midnight) and you want screens off 45 minutes earlier. Bedtime in minutes: 0 × 60 + 20 = 20. Subtract the cutoff: 20 − 45 = −25. Adding a full day of 1440 minutes gives 1415, which is 23 hours and 35 minutes. The tool shows a screen curfew of 23:35, which falls on the evening before. For a bedtime of 22:30 the same 45 minutes would give 21:45.

Try this example →

Common mistakes

  • Entering the bedtime as 10:30 PM or 10.30. Only 24-hour HH:MM works, so 22:30 is correct and the 12-hour form returns nothing.
  • Writing a midnight bedtime as 24:00. Hours go up to 23, so use 00:00 instead.
  • Entering the cutoff in hours. The field is in minutes, so 1 hour must be typed as 60; typing 1 puts the curfew only one minute before bed.
  • Forgetting that a late bedtime pushes the curfew onto the previous calendar day. A curfew of 23:35 for a 00:20 bedtime means 23:35 the night before, not the next evening.
  • Using the result as a fixed prescription. The tool simply subtracts the minutes you choose; it does not know how long you need to fall asleep or what kind of screen use you plan.

Sources

About this calculator

A screen curfew is a fixed cutoff time before bed after which screens (phones, tablets, TV) are put away, based on sleep-hygiene guidance that blue light and mentally stimulating content close to bedtime delay the release of melatonin and make it harder to fall asleep. This calculator simply subtracts your chosen cutoff window from your bedtime to tell you exactly when to stop.

Parents setting rules for kids, and adults trying to improve their own sleep quality, use a screen curfew as a concrete, schedulable habit rather than a vague intention — sleep specialists commonly recommend anywhere from 30 minutes to an hour or more of screen-free wind-down time, and having an exact clock time to aim for makes the habit easier to actually keep.

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Comments (1)

  • Editorial team

    Start from your alarm rather than your habits. If you wake at 06:30 and want eight hours in bed, the bedtime to enter is 22:30, and a 60 minute window then puts the curfew at 21:30. The tool only subtracts minutes from the time you type; it does not know when you actually fall asleep. What do you plan to do in the screen-free hour, and has anything helped you stick to it?

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