Date Calculator: Add or Subtract Days

How does this date calculator work?

It adds or subtracts the years and months first, then the weeks and days, and shows the date you land on with its weekday.

Years and months move by calendar months rather than blocks of 30 days. When the new month is too short for the day you started on, the result stops on that month's last day, so January 31 plus one month is the last day of February. The start date counts as day zero, which means 1 day after a Monday is Tuesday. The calculator runs in your browser and gives the same answer in every time zone.

How do you add days to a date?

Count forward one month at a time: use up the days left in the current month, step through whole months, and finish in the month where the count runs out. Here is how 90 days after March 1 reaches May 30:

1. March 1 to March 31 uses 30 days, leaving 60.
2. April's 30 days bring you to April 30, leaving 30.
3. Thirty more days lands on May 30.

So 90 days after March 1 is May 30, in any year.

The same method works across the end of a year. Remember that February has 29 days in a leap year, so a count that runs through it lands one day earlier than it would in a common year.

How do you add months or years to a date?

Move the month or year forward and keep the same day of the month, unless that day doesn't exist in the new month; then use the month's last day.

That's why adding months and adding days can disagree: three months after March 1 is June 1, which is 92 days later, not 90. January 31 plus one month is February 28, or February 29 in a leap year, and February 29 plus one year is February 28. Excel's EDATE function follows the same month-end rule, so the calculator's answers match it.

What date is 30, 60 or 90 days from today?

The table counts forward from today's date on your device, so it stays current; for any other start date, use the calculator above.

Return windows, notice periods and payment terms are often written this way. If a deadline counts business days instead of calendar days, it lands later, so check which kind the rule means.

How do you subtract days from a date?

Count backward the same way, one month at a time. For 30 days before December 25, going back 25 days reaches November 30, and 5 more reaches November 25.

Choose Subtract in the calculator to count back from a deadline, for example to find when to send a notice that needs 45 days' warning, or to work out the start of a 90-day window that ends today.

What if you need business days instead?

Use the business days calculator when weekends and holidays shouldn't count, because a calendar-day answer lands too early for most work deadlines.

The business days calculator skips Saturdays, Sundays and US federal holidays, counts the working days between two dates, and finds the date a set number of business days away. To count the calendar days between two dates instead, use the day counter.

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