How to use this calculator
Select two dates to compare calendar-day intervals, or add or subtract a duration from a date. Use the weekend option when you want weekday counting rather than all days. Decide whether the endpoints should be included before interpreting the result.
Method and interpretation
A calendar-day difference compares dates, not elapsed hours, so a daylight-saving transition does not turn a day into a fraction. Weekday counting excludes Saturdays and Sundays according to the selected endpoint convention. Adding months and years uses calendar rules rather than fixed 30- or 365-day blocks.
Assumptions and limits
Weekdays are not the same as business days: public holidays and local working schedules are not automatically removed. Month-end dates require a convention when the destination month has fewer days. This tool does not verify legal filing, payment or contract deadlines.
Worked example
From Monday June 1, 2026 to Friday June 5, 2026, the date difference is 4 days. Counting weekdays with both endpoints included gives 5 weekdays. Those are different questions, so choose the endpoint convention that matches your task.