Time Duration Calculator
Add hours, durations, decimal hours, dates
Rules used: 1 hour = 60 minutes = 3,600 seconds; decimal hours = minutes ÷ 60 · Updated Oct 21, 2026
Find how long it is between two dates and times, or what time it will be after adding or taking away hours and minutes.
How to use the Time Duration Calculator
- Pick Between two times and set the start and end date and time.
- Or pick Time plus / minus, enter a time and the hours to add or subtract.
- Read the duration in hours:minutes, decimal hours and minutes.
How to calculate a time duration
Count the whole days between the dates, multiply by 24 hours, then add the difference between the two clock times. From Monday 9:00 AM to Tuesday 2:30 PM: 1 day = 24 h, plus 5 h 30 min = 29:30 (29.5 hours).
What time will it be in X hours?
Use Time plus / minus: 10:45 PM + 3:30 is 2:15 AM the next day.
Frequently asked questions
How many hours are between 9 AM and 5 PM?
8 hours.
Does it handle daylight saving time?
Dates are counted as whole calendar days of 24 hours. On the night clocks change, a real elapsed time is one hour shorter or longer.
More time tools
Results are calculations from the times you enter. Pay figures are gross estimates before tax; your employment contract and local law decide what you are actually owed.