Date Calculator: Add or Subtract Time From Any Date

Pick a start date, choose add or subtract, and enter the years, months, weeks and days. The calculator gives the resulting date, the weekday and how many days it is from the start.

FreeNo sign-upRuns in your browserUpdated 2 Nov 2026
Your resultLive

Estimates only. Check important results before you rely on them.

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How to use this calculator

  1. Pick the start date. It fills with today by default.
  2. Choose Add or Subtract.
  3. Enter the years, months, weeks and days.
  4. Read the new date and its weekday.

The formula

Years and months are added first to the calendar date. If the day does not exist in the new month, the last day of that month is used. Weeks and days are then added as 7 and 1 days.

Worked example

Adding 3 months, 2 weeks and 5 days to 2 November 2026: 3 months gives 2 February 2027, and 19 more days gives Sunday, 21 February 2027, which is 111 days later.

Understanding your result

Adding a month to 31 January gives 28 February (or 29 in a leap year), because February has no 31st. The week number is the ISO week, which starts on Monday.

When to use it

  • Find a due date, a deadline or an expiry date.
  • Plan a notice period or a warranty end.
  • Look back a number of days from today.

Assumptions and limits

Dates use the Gregorian calendar and have no time zone. To count only working days use the Business Days Calculator.

Frequently asked questions

How do I add months to a date?

Add the months to the month number, keeping the day. If the day is too large for the month, the last day of the month is used.

What is 90 days from today?

Enter 90 in the days field with Add selected and today as the start.

Does it handle leap years?

Yes. 29 February is treated correctly.

Can I subtract a date?

Yes. Choose Subtract to go backwards.

What does the week number mean?

The ISO 8601 week of the year, where weeks start on Monday.