Add or Subtract Time Calculator

Everyday Life

The Add or Subtract Time Calculator tells you what time it will be after adding or subtracting a number of hours and minutes from a start time. Enter a 24-hour start time, choose add or subtract, and it returns the new time in both 24-hour and 12-hour formats, plus any day change.

Formula

Resulting time = start time ± (hours and minutes), wrapped within a 24-hour clock
  • Start with the start time in minutes from midnight, then add or subtract the entered hours and minutes.
  • Formula: resulting time = start time ± (hours × 60 + minutes), wrapped within a 24-hour clock.
  • If the result crosses midnight, the 'Day change' output shows how many days forward or back it lands.
  • The start time must be in 24-hour HH:MM format, for example 14:00 for 2 PM.

Example Calculation

Inputs
  • Start time (24-hour, HH:MM): 14:00
  • Operation: add
  • Hours: 3
  • Minutes: 45

Adding 3 hours 45 minutes to 14:00 gives 17:45 (5:45 PM) on the same day.

Frequently asked questions

What time format should I use?
Enter the start time in 24-hour HH:MM format, such as 09:30 or 14:00. Results are shown in both 24-hour and 12-hour formats.
How do I subtract time?
Choose 'Subtract (−)' in the Operation field, then enter the hours and minutes to take away from the start time.
What if the result crosses midnight?
The 'Day change' output tells you whether the result lands on the same day, the next day, or a previous day.
Can I add more than 24 hours?
Yes. Larger durations roll over correctly, and the day change output reflects how many days were added or removed.
Does it handle minutes over 59?
Yes. Extra minutes carry into hours automatically when the total is computed.

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