About Duration Calculator

Calculate the duration between two dates or times. Part of the DevTools Surf developer suite. Browse more tools in the Date / Time collection.

Use Cases

• Calculating sprint durations for agile project planning
• Computing SLA response times from incident timestamps
• Measuring elapsed time between deployment events
• Determining contract or license period lengths

Tips

• Enter two dates to see the exact duration between them
• View results in multiple units: days, hours, minutes, seconds
• Use this to calculate project timeline spans accurately

Fun Facts

• The ISO 8601 duration format (e.g., P3Y6M4DT12H30M5S) was standardized in 1988 and is used by many programming language date libraries.
• A tropical year is actually 365.24219 days, which is why we need leap years and why the Gregorian calendar skips 3 leap years every 400 years.
• The Unix epoch (January 1, 1970, 00:00:00 UTC) is the reference point for most computer time calculations worldwide.

FAQ

Can I subtract two dates?

Yes — date1 minus date2 gives the duration. Output in human-readable (2 years 3 months 15 days), ISO 8601 (P2Y3M15D), and pure seconds/minutes/hours.

What about times within a day?

Yes — input two timestamps on the same day, get the hours:minutes:seconds duration. Useful for billing or performance tracking.

Handle DST transitions?

Yes — 'spring forward' loses an hour; 'fall back' gains one. The duration reflects wall-clock time, not actual elapsed seconds. Toggle to use UTC for DST-free math.

Negative durations?

Supported — if date1 is before date2. Useful for 'how overdue is this task?' scenarios.