CALCULATOR · Date & Time
Date Calculator
Work out the days between two dates, add or subtract days, weeks, months and years, count down to a date, and see the weekday and week number.
Show formula
Inputs
Calendar
Every date field, picker and result uses this calendar.
Result
Your result appears here
Pick two dates to see the span between them.
How it works
- Pick the question you want answered: the span between two dates, adding or subtracting time, a countdown, or the facts about one date.
- Enter your dates — the calendar selector switches the whole calculator between Gregorian, Jalali/Shamsi and Hijri.
- Read the result plus the weekday, ISO week number and day of the year.
Frequently asked questions
Why is this one page instead of separate pages per question?
Adding days, counting days between dates and counting down to a date are the same calendar arithmetic asked four ways. One accurate page you can switch modes in is more useful than four near-identical pages, and it keeps every answer consistent.
What happens when I add a month to January 31?
The result becomes February 28 (or 29 in a leap year). The target day does not exist, so the calculator clamps to the last day of that month — the standard convention — and tells you it did.
Do daylight-saving changes shift the answer?
No. Every date is reduced to UTC midnight before any arithmetic, so a span that crosses a clock change still returns whole days.
How is the week number calculated?
Following ISO-8601: weeks start on Monday, and week 1 is the week containing the first Thursday of the year. That is why January 1 can belong to week 52 or 53 of the previous year.
Are the start and end dates counted?
The difference counts the midnights between the two dates, so the same day twice gives 0 and consecutive days give 1. The Business Days Calculator uses inclusive counting instead, because that is what people expect when counting working days.
Examples
- What date is 90 days after 1 March 2026?
- Saturday, 30 May 2026 — day 150 of the year.
- What date was 6 weeks before 25 December 2026?
- Friday, 13 November 2026, 42 days earlier.
- What date is 3 months after 31 January 2026?
- 30 April 2026. April has no 31st, so the result moves to the last day of the month.
Related calculators
- Date Difference CalculatorThe exact difference between two dates in days, weeks, months and years — leap-year accurate.Date & Time
- Business Days CalculatorCount working days between two dates, with custom weekends and holiday exclusions.Date & Time
- Time CalculatorAdd up hours and minutes, measure the time between two times including overnight shifts, total a work week with breaks and overtime, and add or subtract time from a clock.Date & Time
- Age CalculatorYour exact age in years, months and days — plus totals, birth weekday and a next-birthday countdown.Date & Time
- Time ConverterSeconds, minutes, hours, days, weeks, months and years converted exactly.Converters