Date & duration calculator
Compare two calendar dates with the counting rules shown, or move a date by ordinary days or Monday–Friday weekdays.
The signed result is this end date minus the start date.
The end date comes this many calendar days after the start date.
- Elapsed days (signed: End − Start)
- +151
- Absolute duration
- 21 full weeks, 4 remaining days
- Weekdays elapsed (signed; Start included, End excluded)
- +108
- Calendar days including both dates
- 152
- Weekdays including both dates
- 109
Monday–Friday counts exclude Saturday and Sunday but not public holidays. All arithmetic uses calendar dates, not clock time.
Included
- Gregorian date-only calculations from 1 January 1900 through 31 December 2100
- Signed elapsed calendar days and absolute full weeks plus remaining days
- Counts that include both endpoint dates
- Monday–Friday elapsed and inclusive counts
- Adding or subtracting calendar days or Monday–Friday weekdays
Not included
- Public holidays, local holiday calendars and custom working weeks
- Clock times, partial days, time zones and daylight-saving changes
- Recurring dates, months or years as shift units
- Legal deadlines, payroll dates, leave entitlement or compliance advice
What this means
The comparison uses End − Start. A later end date gives a positive elapsed count; an earlier end date gives a negative count. Full weeks and remaining days use the absolute distance so they describe its size rather than its direction.
The elapsed weekday count is half-open: moving forward, it includes the start date and excludes the end date, then keeps the same rule with the sign reversed when the dates are reversed. The two inclusive counts instead cover both endpoint dates and are always non-negative.
A weekday shift counts Monday through Friday only. The starting date is not the first shifted day. From a Saturday or Sunday, adding reaches the next Monday and subtracting reaches the previous Friday; shifting by zero leaves any date unchanged. Public holidays are not known.
Formula & worked example
elapsed days = End date − Start date inclusive calendar days = |elapsed days| + 1 full weeks = floor(|elapsed days| ÷ 7) remaining days = |elapsed days| mod 7 elapsed weekdays = signed count of Monday–Friday dates in [Start, End) inclusive weekdays = Monday–Friday dates from the earlier through the later date, including both endpoints
Monday 3 March 2025 to Monday 10 March 2025
- Elapsed calendar days: 10 March − 3 March
- +7 days
- Full weeks and remaining days
- 1 week, 0 days
- Monday–Friday dates in [Start, End)
- +5 weekdays
- Monday–Friday dates including both Mondays
- 6 weekdays
The dates are 7 calendar days apart. The half-open elapsed interval contains 5 weekdays, while the inclusive range contains 6 weekdays because it includes both Mondays.
How this calculation works
The calculation follows the formulas, definitions and assumptions explained on this page. The references below support the method and any stated boundaries.
Official sources
- ISO — ISO 8601 date and time format — Unambiguous Gregorian calendar dates written in year-month-day order; the inclusive and weekday counting rules are stated product choices