Time Duration Calculator

The Time Duration Calculator helps you find the difference between two points in time or add/subtract a duration from a given time.

Start Time
End Time

Understanding Time Duration

Calculating time durations is useful for planning schedules, tracking work hours, or figuring out elapsed time for events. This calculator can find the difference between two times or calculate a future/past time by adding/subtracting a duration.

How the Time Duration Calculator Works

Duration Between Two Times:

  1. Convert both start and end times to total seconds from midnight (00:00:00).
  2. If the end time is on the next day (spans midnight), add 24 hours (86,400 seconds) to the end time's total seconds.
  3. Subtract the start time's total seconds from the end time's total seconds.
  4. Convert the resulting difference in seconds back to HH:MM:SS format.

Adding/Subtracting Duration:

  1. Convert the initial time to total seconds from midnight.
  2. Convert the duration to add/subtract into total seconds.
  3. For addition, add the duration seconds to the initial time seconds.
  4. For subtraction, subtract the duration seconds from the initial time seconds.
  5. Handle rollovers: If the result is negative (for subtraction) or exceeds 24 hours (for addition), adjust by adding/subtracting multiples of 86,400 seconds (24 hours) and track day offsets.
  6. Convert the final total seconds back to HH:MM:SS format.

Tips for Using the Time Duration Calculator

24-Hour Format

All time inputs should be in 24-hour format (e.g., 1 PM is 13:00).

Spanning Midnight

When calculating the duration between two times, if the end time is on the following day (e.g., start 10 PM, end 2 AM), ensure you check the "End time is on the next day" box for an accurate calculation.

Large Durations

When adding or subtracting large durations that might span multiple days, the calculator will indicate the day offset (e.g., "+1 day", "-2 days").

Frequently Asked Questions

How do I convert 12-hour AM/PM time to 24-hour format?

For AM times, if it's 12 AM (midnight), it's 00 hours. For 1 AM to 11 AM, the hour remains the same. For PM times, if it's 12 PM (noon), it's 12 hours. For 1 PM to 11 PM, add 12 to the hour (e.g., 5 PM is 17:00).

What if I need to calculate durations involving dates as well?

This calculator focuses on time within a 24-hour cycle or simple day offsets. For calculations involving specific dates over longer periods, you would typically use a date difference calculator.