Date Calculator
Free to use, with no sign up. Your entries stay in this browser; calculations run on your device.
Result
Exclusive days = later date − earlier date, measured in calendar days. Inclusive days = exclusive days + 1. Weekdays filter out Saturdays and Sundays. Reversing the dates makes the count negative.
U.S. Naval Observatory gives the Gregorian leap-year rule. Endpoint counting and month-end clamping are the conventions used here.
Worked example: 2024-01-01 to 2024-01-08 = 7 days exclusive or 8 days inclusive; weekdays only = 5 exclusive or 6 inclusive.
Add or subtract a date
New date
Days: date + amount. Weeks: date + 7 × amount. Months and years move the calendar month/year, then clamp the original day to the last day of the target month.
U.S. Naval Observatory gives the Gregorian leap-year rule. Endpoint counting and month-end clamping are the conventions used here.
Worked example: 2024-01-31 + 1 month = 2024-02-29; 2024-02-29 + 1 year = 2025-02-28.
Dates use the Gregorian calendar for years 0001–9999. Calendar days do not depend on daylight-saving time. Exclusive counting excludes the earlier endpoint and includes the later endpoint; equal dates count as zero exclusive or one inclusive. Weekday mode excludes weekends only.
How to use this tool
Enter two dates to count days, or use the second form to add or subtract calendar units. Choose whether to include both endpoints and whether to count weekdays only.
Frequently asked questions
Does this count holidays?
No. Weekdays only means Monday through Friday, including public holidays. It is not a business-holiday calendar.
What does inclusive mean?
Inclusive counts both endpoint dates. Exclusive excludes the earlier endpoint and includes the later one. Reversed inputs return a negative count; equal dates return zero exclusive or one inclusive, unless weekday filtering removes that day.
What happens at the end of a month?
Adding months or years preserves the day where possible, otherwise uses the last day of the destination month. Each operation clamps once, so adding two months in one step can differ from adding one month twice.