📅 Date Difference Calculator
Days between two dates. Runs privately in your browser.
Exact calendar arithmetic, nothing rounded
The calculation is exact calendar arithmetic: the difference between the two dates divided by the exact milliseconds in a day, rounded — no approximations, no '30-day months'. February, leap years and month lengths are all handled by the underlying date logic.
The calculator is direction-aware: if the end date is before the start date it says so and still gives the absolute gap, which prevents the classic negative-days confusion when filling in forms.
Days = |dateB − dateA| ÷ 86,400,000 (ms per day). Weeks = days ÷ 7, shown to one decimal.
Spring to summer, and the run-up to Christmas
From 1 March 2026 to 15 June 2026 is 106 days — about 15.1 weeks. From 9 September 2026 to 24 December 2026 is 106 days too (the calculator shows it in one click). A 90-day notice period starting 15 August ends 13 November — set the two dates and read off the confirmation.
The inclusive-counting trap
- Off-by-one when counting inclusively. Days *between* dates excludes the start day; a '3-night stay' from the 10th to the 13th spans 3 days but touches 4 calendar dates. Decide which convention you need.
- Ignoring timezones on dates entered as local midnight versus UTC — this calculator anchors both dates at local midnight, so no gap appears.
- Forgetting that 'weeks' output is decimal, not whole-week-plus-remainder.
- Using the tool for business-day counts — it counts calendar days; weekends and holidays are included.Mixing up calendar days with banking days — loan interest, clearing times and legal notice periods often count business days, which this tool deliberately does not.
Date questions
Are weekends and holidays counted?
Yes — this is pure calendar-days arithmetic. For business-day differences, subtract weekends manually or use a working-day tool.
What if I put the dates in the wrong order?
The result is the same absolute gap; the calculator notes that the end precedes the start.
Can I count the days between two dates a year apart?
Yes — any pair of dates works, including across leap years.
Why do I get 1 day between today and tomorrow here, but '1 day' elsewhere means two calendar dates?
Conventions differ: elapsed time (this tool) versus inclusive counting (hotel nights). Read the form you're filling in.
Does it handle different timezones?
Both dates are treated as local midnight, which is what date-only fields imply — no timezone drift.
Does the calculator show weeks and months?
It shows the days gap plus a decimal-weeks conversion. For a years/months/days breakdown of a person's age, use the Age Calculator, which does calendar-accurate borrowing.
Related date tools
Tip: double-check inputs before relying on results for important decisions.