Date Calculator

Difference between dates: enter a start and an end date and the calculator shows the gap in years, months and days, and as total days and weeks. The end date is exclusive by default (1 to 10 January is nine days), which matches how most contracts, rentals and hotel nights are counted; tick the option to include the end date when you want the count of calendar days covered, as for a course or a holiday.

Add or subtract: enter a date and a number of days, weeks or months to find the resulting date. Ninety days from 3 September is 2 December; three months from 31 January is 30 April, since April has no 31st. Months are added calendar-wise, then clamped to the last valid day, which is the convention used by most legal and financial systems.

The business-day option skips Saturdays and Sundays. It does not know your public holidays, since those vary by country and year, so add them manually if a deadline falls near one. Leap years are handled properly (a year divisible by 4 is a leap year unless it is divisible by 100 and not by 400, so 2000 was and 2100 will not be), and the calculator uses real month lengths rather than 30-day approximations, so counting months across February is exact.

Dates here are calendar dates in your device's time zone with no time-of-day component, so daylight-saving changes and time zones do not affect the day count. All calculations use the Gregorian calendar, which is the civil calendar almost everywhere; converting to or from Hijri, Hebrew or other calendars requires a dedicated converter. For counting hours and minutes rather than days, the time unit converter handles the arithmetic.