Date Difference Calculator
Calculate the exact difference between two dates or add and subtract days, weeks, months and years from any date. Includes business days, weekends and quick presets
How the Date Difference Calculator Works
Enter a start date and an end date and the tool returns the gap in years, months and days, plus running totals in weeks, days, hours, minutes and seconds. It also splits the period into business days (Monday-Friday) versus weekend days, and tells you what day of the week each end of the range falls on.
Reverse the dates if you put them in the wrong order; the tool flags it but still gives you the correct figure. Tick 'include end date' when you are counting consumable items per day (a 7-day medication course, for example), because that calculation needs both bookend days counted. Leave it unticked when calculating an interval (the duration of a project, for example).
Common Use Cases at a Glance
| Scenario | What to Calculate | Tip |
|---|---|---|
| Project planning | Working days between kick-off and deadline | Use [Work Days Calculator](/work-days-calculator) to also strip bank holidays |
| Pregnancy tracking | Days from first day of last period | 40 weeks (280 days) is the standard due-date estimate |
| Visa applications | Days remaining on a 90-in-180 rule | Set 'include end date' on; the day you arrive counts |
| Anniversary maths | Years, months and days for a card | Use start date = wedding day, end date = today |
| Notice periods | Calendar days from notice given to last day | Most UK contracts count weekends, so leave business days info-only |
Add or Subtract Days, Weeks, Months or Years From a Date
Switch tabs to add or remove a duration from any starting date. Useful for working out the date 90 days after a contract is signed, or the end of a 12-week probation period that started on 6 January. The tool returns the resulting date and the day of the week, so you can spot whether your deadline falls on a weekend.
Adding 'months' uses calendar months rather than 30-day blocks. So 31 January plus one month becomes 28 February (or 29 February in a leap year), not 3 March. This matches how UK contract law typically interprets monthly notice.
Frequently Asked Questions
Why does the year/month/day breakdown look different to a simple subtraction?
Months are different lengths, so the breakdown borrows days from the previous month when needed. From 31 January to 1 March is 0 years, 1 month, 1 day in 2026 (a non-leap year), but the same dates in 2024 (a leap year) give 1 month and 0 days. The total day count is unaffected; only the years/months/days split changes.
How does the tool handle leap years?
Each year is checked individually using the Gregorian rule: divisible by 4 = leap, except century years which must be divisible by 400. So 2000 was a leap year but 2100 will not be. Dates before 15 October 1582 use the same maths, even though England was actually still on the Julian calendar until 1752; for genealogy work spanning that gap, treat results as approximate.
What is the difference between business days and working days here?
This tool excludes Saturdays and Sundays only. It does not subtract bank holidays. If you need a working-day count that strips bank holidays as well, use the [Work Days Calculator](/work-days-calculator), which has the UK 2026 calendar built in (1 Jan, 3 Apr Good Friday, 6 Apr Easter Mon, 4 May, 25 May, 31 Aug, 25 Dec, 28 Dec).
Can I include time of day, not just dates?
This tool works at full-day resolution. For sub-day intervals, the totalHours, totalMinutes and totalSeconds figures are derived from whole days. To time something like a 6-hour shift across midnight, the [Work Hours Calculator](/work-hours-calculator) is a better fit.
Related Tools
Work Days Calculator
Calculate working days between two dates excluding weekends and UK bank holidays with full breakdown of total, weekend and holiday days
Days Until Calculator
Count down the days until any date or event. Quick presets for Christmas, New Year, Easter and more. Shows weeks, months and sleeps
Age Calculator
Calculate your exact age in years, months and days. Plus total days alive, zodiac sign, Chinese zodiac, generation and next birthday countdown
Week Number Calculator
Find the ISO week number for any date plus day of week, day of year and days remaining with optional year calendar view