Add or Subtract Time

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Add or subtract hours, minutes and seconds from any start time and get the result in 24-hour and 12-hour formats, plus a note if it crosses midnight. Free and instant.

Resulting time –
In 24-hour format –
In 12-hour format –
Total duration –
Day change –
Time wraps around a 24-hour clock; the day-change note shows whether the result lands on the same day, the next day or a previous day.

About Add or Subtract Time

This calculator adds or subtracts hours, minutes and seconds from any start time on the clock. Enter a time, choose add or subtract, set the duration, and the result appears in both 24-hour and 12-hour formats — no more counting forward on your fingers past noon or midnight.

Time wraps around a 24-hour clock, so the tool also tells you whether the result lands on the same day, the next day or a previous day. That day-change note matters for shift planning, cooking timers that run overnight, medication schedules and travel arithmetic.

Alongside the resulting time you see the total duration applied, which is handy when you combine hours, minutes and seconds in one operation. The calculator is free, updates as you type and runs entirely in your browser.

How to use Add or Subtract Time

  1. Enter the start time.
  2. Choose whether to add or subtract.
  3. Fill in the hours, minutes and seconds to apply.
  4. Read the resulting time in 24-hour and 12-hour formats, plus the day-change note.

Frequently asked questions

The clock wraps around 24 hours and the calculator flags the change — “Next day” when an addition passes midnight, “Previous day” when a subtraction goes back beyond it, or “Same day” otherwise.

Yes. All three fields are combined into a single duration, and the total applied is shown with the result so you can verify exactly what was added or subtracted.

Schedules, tickets and devices mix the two conventions. Displaying 18:45 and 6:45 PM together removes any ambiguity when you copy the result somewhere else.

Yes. Durations longer than a day simply wrap the clock multiple times, and the day-change note reflects how many days the result moved.
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