Duration Calculator

Overview

• Enter two date/times (start and end), and calculates the difference both as a breakdown in days/hours/minutes/seconds and as totals in each unit.
• Calculates based on the elapsed milliseconds between the two date/times without considering the calendar, so leap years and differing month lengths are reflected as-is in the elapsed time.
• Works even if the end date/time is before the start; in that case the absolute value (magnitude of elapsed time) is shown.

Usage

1. Enter a date/time into both "Start date/time" and "End date/time" (ISO 8601 format is recommended).
2. Click "Calculate".
3. The breakdown in days, hours, minutes, and seconds, along with totals in each unit, is displayed.

Example

Start: 2026-01-01T00:00:00Z / End: 2026-01-03T05:30:15Z

2d 5h 30m 15s

Use Cases

• Calculating elapsed or remaining days from a project's start and end dates
• Precisely determining an event's duration down to the minute and second, from its start and end times
• Checking the difference between two timestamps, such as a processing time recorded in a system log

FAQ

Notes

• An ISO 8601 string without an explicit timezone (e.g. 2026-01-01T00:00:00) is interpreted in the browser's local timezone. Append "Z" if you want it treated as UTC.
• The calendar is not considered. This is a simple difference based on elapsed milliseconds, not a calendar-aware calculation like "1 month".
• The calculation result exists only on the page and is lost on reload, so copy and save it if you need to keep it.