Date Difference Calculator
Last reviewed: October 14, 2026
Count the days between any two dates and see the total broken into years, months, weeks and days. The calculator also splits those days into weekdays and weekend days, and counts the business days left once the public holidays of the country you pick are taken out (it starts on the United States), so a calendar span and a working-day span sit side by side.
Useful for project spans, contract terms, anniversaries and the plain question of how many days are left until a date. When a period is stated in business days, such as a service-level target, the business days between dates calculator is the closer fit.
Worked example: a consulting contract
A consulting contract runs from Sunday, March 1, 2026 through Tuesday, December 15, 2026. Both dates are days of the contract, so turn Include start date on and leave Include end date on. The calculator counts 290 days, which it breaks down as 9 months, 2 weeks and 1 day. Of those, 207 are weekdays and 83 fall on a weekend. On the US federal calendar 7 holidays land on a weekday inside the term, which leaves 200 business days: the figure to plan billable days against. With the toggles as the calculator opens (start date off), the same dates give 289 days, the plain difference between them, and 200 business days. Counting the start date adds a business day only when the start date is itself one; this contract starts on a Sunday.
When calendar days are the right frame
Calendar days fit whenever every day counts, whether or not anyone is at work: rent or interest that accrues per day, a policy or subscription term, an age, a countdown to an anniversary. Business days fit only when the contract, rule or statute that sets the period says so, so read how it defines a day before you choose. The calculator shows both counts for the same two dates, which makes the gap between them visible before you commit to one.
How leap years and DST change the answer
A span that crosses 29 February in a leap year has one more day than the same span in another year. Tuesday, February 1, 2028 to Wednesday, March 1, 2028 is 29 days; Monday, February 1, 2027 to Monday, March 1, 2027 is 28 days. Daylight saving time does not change the count. The calculator compares calendar dates, not clock times, so a span that includes a clock change still counts whole days.
The Include start date and Include end date toggles
The calculator opens with Include start date off and Include end date on, so the count equals the end date minus the start date. From Sunday, March 1, 2026 to Wednesday, March 4, 2026 it counts 3 days, the nights of a stay that checks in on the first date and out on the second. That is the counting rule the Federal Rules of Civil Procedure set for periods stated in days: Rule 6(a)(1) excludes the day of the event that triggers the period and includes the last day. Turn Include start date on when the first day itself counts, such as the first day of a contract or of coverage; with both toggles on, a single date counts as one day. Turn Include end date off as well to count only the days strictly between the two dates, which is how the business days between dates calculator opens. Rule 6(a)(1)(C) also moves a last day that falls on a Saturday, Sunday or legal holiday to the next day that is not one. This calculator does not; the response deadline calculator shows that next business day.
Sources for these rules
- Federal Holidays: a Saturday holiday is observed on the preceding Friday (5 U.S.C. 6103(b)), a Sunday holiday on the following Monday (E.O. 11582, section 3(a)) (U.S. Office of Personnel Management)
- Federal Rules of Civil Procedure, Rule 6(a)(1): exclude the trigger day, count every day, include the last day unless it is a Saturday, Sunday or legal holiday, then run to the next day that is not; (a)(6): legal holidays are the listed federal holidays, days declared by the President or Congress and, for periods measured after an event, state holidays; (d): 3 days added after service by mail (U.S. Government Publishing Office (govinfo))
Checked October 9, 2026. All sources
For informational purposes only
This calculator provides general estimates based on business day counting rules. It does not constitute legal advice. Deadlines in legal, regulatory, or contractual matters may be subject to jurisdiction-specific rules, court orders, or statutory exceptions. Always verify critical deadlines with a qualified professional.