Time Duration Calculator — Free Online
Calculate the exact time duration between two timestamps in hours, minutes, and seconds. Handles overnight calculations and shows total minutes and decimal hours simultaneously.
How to Use the Time Duration Calculator
- Enter your start date and time using the datetime picker in the "Start Date & Time" field
- Enter your end date and time in the "End Date & Time" field
- Click "Calculate Duration" to see the exact time span
- The result shows hours, minutes, and seconds — plus total minutes and decimal hours
- Overnight durations (crossing midnight) are handled automatically
How the Time Duration Calculator Works — The Formula
Duration = End DateTime − Start DateTime
Total Seconds = (End − Start) in seconds
Total Minutes = Total Seconds / 60
Total Hours (decimal) = Total Seconds / 3600
Formatted:
Hours = ⌊Total Seconds / 3600⌋
Minutes = ⌊(Total Seconds mod 3600) / 60⌋
Seconds = Total Seconds mod 60
Overnight: automatically handled — no 24h modulo error
Formula validated by Vipul Jaganiya, Computer Science expert in Calendar Mathematics and Timezone Engineering.
Real-World Examples
| Start | End | Duration | Use Case |
|---|---|---|---|
| 2026-05-26 09:00 | 2026-05-26 17:30 | 8h 30m 0s | Standard workday |
| 2026-05-26 22:00 | 2026-05-27 06:00 | 8h 0m 0s | Overnight shift |
| 2026-05-26 10:15 | 2026-05-26 11:45 | 1h 30m 0s | Meeting duration |
| 2026-05-01 00:00 | 2026-05-31 23:59 | 743h 59m 0s | Entire month of May |