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Add or Subtract Days

Find the date a number of days, weeks, months or years before or after any date. Count calendar days or business days only, for deadlines, notice periods and due dates.

Runs on your device. Nothing you enter is sent to a server.

A date calculator for days before and after a date

This date calculator adds or subtracts any mix of years, months, weeks and days from a start date. Use it to find a deadline 30 days from today, the end of a 6 month notice period, a due date 90 days after an invoice, or the date 2 weeks before an event. The result shows the weekday, the ISO date and how many calendar days it is from the start.

Switch on business days only when the days you count are working days. The calculator then skips weekends and, if you like, US federal holidays, which is how many payment terms and filing deadlines are counted.

How the date is worked out

The calculator first moves by whole years and months on the calendar, then by weeks and days. The start date itself is never counted, so 1 day after today is tomorrow.

Step 1
Start date ± (years × 12 + months)
Step 2
± (weeks × 7 + days)

The month-end rule

Months have 28 to 31 days, so adding a month is not the same as adding 30 days. When the start day does not exist in the target month, the date moves to the last day of that month:

  • January 31, 2026 + 1 month = February 28, 2026 (February 2026 has 28 days).
  • January 31, 2028 + 1 month = February 29, 2028 (2028 is a leap year).
  • March 31 + 1 month = April 30, and August 31 + 1 month = September 30.
  • February 29, 2028 + 1 year = February 28, 2029.

This is the same rule spreadsheets use for EDATE and most contracts use for monthly terms. If you need exactly 30 days instead, enter 30 in the days field.

Examples

  • Net 30 payment terms: invoice date plus 30 days gives the payment deadline.
  • Return windows: purchase date plus 14 or 30 days shows the last day to send something back.
  • Counting back: subtract 6 weeks from an event to find when to send invitations, or 10 business days from a filing date to know when the draft must be ready.
  • Anniversaries and renewals: add 1 year to a start date, or 6 months for a half year review.

The questions people ask most have a page of their own with the answer for today and a table of the dates around it, such as what date is 90 days from today:

How to use the add or subtract days calculator

  1. 1Pick the start date, or press Today for the current date.
  2. 2Choose Add or Subtract and type the years, months, weeks and days, in any combination. The chips fill in common amounts in one tap.
  3. 3Tick business days only if weekends should not count. Read the result date and weekday, then copy it or share a link with your numbers.

Frequently asked questions

What date is 90 days from today?

Leave the start date on today, choose Add and enter 90 in the days field, or press the +90 days chip. The result shows the date with its weekday. The start day itself is not counted, so 90 days after Monday is a Sunday, 12 weeks and 6 days later.

What happens when I add a month to January 31?

The result is the last day of February: February 28, or February 29 in a leap year. A month is added on the calendar, and when the target month is too short, the date is moved back to that month's last day. Adding one month to March 31 gives April 30 for the same reason.

In which order are years, months, weeks and days added?

Years and months first, then weeks and days. So January 31 plus 1 month and 1 day is March 1: one month gives February 28, one more day gives March 1. Counting the days first would give a different date, which is why the order is fixed and shown here.

How do business days work in this calculator?

With "Business days only" on, the days you enter skip Saturdays and Sundays, and US federal holidays too if you tick that box. The start date is not counted. Five business days after a Friday is the next Friday. Years, months and weeks still move on the calendar first.

Is the start date counted?

No. Adding 1 day to today gives tomorrow, the same way a deadline "in 10 days" is counted. If your rule counts the start day as day 1, add one day less.