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Date calculator

Add or subtract years, months and days from a start date and see the resulting date and its weekday.

Result date

Invalid

Pick a valid start date.

Awaiting input
Operation
Add · subtract
Units
Y · M · D

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Guides

This date calculator counts forward or back from any date. Pick a start date (today is filled in for you), choose Add or Subtract, and enter years, months and days. You get the full date with its weekday, plus the ISO form (YYYY-MM-DD) to copy. Use it for deadlines, notice periods, warranty end dates, or just to see which weekday a date lands on.

How to use the date calculator

  1. Pick the start date. It defaults to today.
  2. Choose Add or Subtract.
  3. Fill in any mix of years, months and days. It starts at 7 days.
  4. Read the result. Click it to copy the long date, or use Copy ISO for YYYY-MM-DD.

How date arithmetic works

Years and months go first, then days. If the day of the month doesn't exist in the target month, the calculator uses that month's last day, so January 31 plus one month is February 28 (29 in a leap year), not March 3. The days are added after that, rolling over months and years as needed. Every count is in calendar days; weekends and holidays aren't skipped. Results must fall between the years 1 and 9999.

Common date calculation scenarios

  • A deadline 90 days after today or after a contract start date.
  • An expiry date a set number of months out.
  • The date someone turns 18, counted from their birthdate.
  • Which weekday a future date falls on.

Frequently asked questions

Can I add months and days at the same time?

Yes. Fill in any combination. Years and months are applied first, then the days.

How does the calculator handle month-end dates?

It uses the last day of the result month. One month after January 31 is February 28, or February 29 in a leap year, rather than spilling into March.

Does the date calculator account for leap years?

Yes. It follows the Gregorian calendar rules built into your browser, so February 29 only appears in leap years.

Does it skip weekends or holidays?

No. It counts calendar days only. For business days you'll need to adjust by hand.

Can I subtract dates to find a duration?

Not here. To find the gap between two dates, use the Time Between Dates tool on this site.

Built and maintained by Bipul Kumar. Found a wrong number or a broken result? Tell me and I'll fix it.