Date Difference Calculator

Runs in browser Utilities

Compute the duration between two dates or timestamps, including business days, and express it as a calendar breakdown and in total days/hours/minutes/seconds.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

What is an ISO 8601 timestamp, and how does it relate to Unix time?

ISO 8601 writes a moment as 2026-09-23T10:15:00+03:00 — largest unit first, with an explicit UTC offset or Z — so it sorts as text and is unambiguous across locales; RFC 3339 is the Internet profile APIs use. Unix time is the same moment as a count of seconds (or milliseconds in JavaScript) since 1970-01-01T00:00:00Z, with no time zone at all. Most date bugs are an offset applied twice or a local time stored as if it were UTC.

How to use Date Difference Calculator

  1. Enter the start and end dates (ISO, epoch or "now").
  2. Choose the calendar timezone and the weekend definition.
  3. Read the breakdown and totals; copy the ISO duration if you need it in an API.

Date Difference Calculator features

  • Calendar breakdown in years, months, days, hours, minutes and seconds
  • Totals in days (with decimals), weeks, months, hours, minutes and seconds
  • Business days with configurable weekends (Sat–Sun, Fri–Sat, Fri, Sun)
  • Inclusive end-day option
  • ISO 8601 duration output (P1Y1M15DT8H30M)
  • Timezone-aware so day boundaries are correct

Date Difference Calculator example

Project duration

Input:

2024-01-31T09:00:00+03:00 → 2025-03-15T17:30:00+03:00 · Asia/Riyadh

Output:

1 year, 1 month, 15 days, 8 hours, 30 minutes
Total days 409 · Business days 292 · P1Y1M15DT8H30M
The breakdown is counted forward from the start date: whole years and months first, with 31 January clamped to 28 February 2025, then whole days, then the remaining hours and minutes.
  1. 1Start date2024-01-31 09:00
  2. 2+ 1 year 1 monthFebruary 2025 has no day 31, so the day is clamped to 28, the month’s last day.2025-02-28 09:00Month end clamped
  3. 3+ 15 daysWhole days, as many as fit before the end.2025-03-15 09:00
  4. 4+ 8 h 30 minThe rest of the time reaches the end date.2025-03-15 17:30

Then:P1Y1M15DT8H30M: 1 year, 1 month, 15 days, 8 hours, 30 minutes

Counted on the calendar of Asia/Riyadh (+03:00), the example’s calendar timezone; another zone can split the days differently. “Total days” 409 (409.35 exact) is elapsed time, not this breakdown.

Frequently asked questions about Date Difference Calculator

How is the calendar breakdown computed?

Whole years and months are added to the start date on the calendar of the selected timezone, with the day clamped to the end of a shorter month, so 31 January → 28 February counts as 1 month (in a leap year it is 28 days, and the month is complete on 29 February). The remaining whole days follow, then hours, minutes and seconds. Totals in days, weeks, hours, minutes and seconds count elapsed time, and Total days also shows the exact decimal value.

What counts as a business day?

Every calendar day after the start date up to and including the end date that is not a weekend. Choose Saturday–Sunday, Friday–Saturday (Gulf region), Friday-only or Sunday-only weekends; public holidays are not excluded.

Why does the timezone matter?

Calendar dates change at midnight local time, so the number of days between two instants can differ by one depending on the zone. Elapsed hours and seconds never change.

What does "Count the end day as a full day" do?

It adds 24 hours to the end date, so a hotel stay from 1 March to 3 March is reported as 3 days instead of 2 (inclusive counting).

Is the ISO 8601 duration exact?

It mirrors the calendar breakdown (P1Y1M15DT8H30M). Because months vary in length it is a description of the difference, not an absolute number of seconds.

References