Calculator
How to add or subtract days from a date
Pick a start date, choose Add or Subtract, enter an amount and pick a unit. The calculator shows the resulting date, the day of the week and where it sits in the year. The start date itself is not counted as day 1, so 1 day after Monday is Tuesday.
Worked examples
- 90 days from 3 November 2026 is Monday 1 February 2027.
- 6 months before 31 August 2026 is 28 February 2026, because February is shorter and the result moves to the last day of the month. In a leap year it would be 29 February.
- 5 business days after Friday 6 November 2026 is Friday 13 November 2026.
Days, weeks, months and years behave differently
Days and weeks are exact: 30 days is always 30 days. Months and years follow the calendar, so 1 month after 15 January is 15 February whatever the month length. If the target month is too short, the result is the last day of that month. Business days skip Saturdays and Sundays, like Excel’s WORKDAY function. For a count that also skips public holidays, use the Business Days Calculator.
To check your answer, put both dates into the Days Between Dates Calculator.
Everything is calculated in your browser. The dates you enter are never uploaded or stored on our servers; they only appear in a link if you choose “Copy link to this result”.
What this is used for
- Deadlines: “due in 30 days”, “payable within 60 days”, “respond within 10 business days”.
- Notice periods and probation: add 1, 3 or 6 months to a start date.
- Warranties and trials: add 90 days or a year to a purchase date.
- Planning: find the date 12 weeks away, then use the Weeks Between Dates Calculator to see the ISO week numbers.
- Age on a date: the Age Calculator handles birthdays and milestone dates.
Frequently asked questions
What is the date 90 days from today?
Leave the start date as today, enter 90 with the unit set to days and choose Add. The result shows the date and the day of the week.
How do I subtract days from a date?
Switch the operation to Subtract. For example, 30 days before 1 March 2026 is 30 January 2026.
Is the start date counted as day 1?
No. Day 1 is the day after the start date. If you need to count the start date, subtract one day from your amount.
What happens when I add a month to the 31st?
The result becomes the last day of the next month if it is shorter, so 31 January plus 1 month is 28 February, or 29 February in a leap year.
Can I add business days?
Yes. Choose business days as the unit. Weekends are skipped, but public holidays are not. Use the Business Days Calculator when holidays matter.
More date & time calculators
- Date & Time Difference CalculatorThe exact gap between two dates and times, with time zones.
- Days Between Dates CalculatorCount the days between any two dates, with or without the end date.
- Business Days CalculatorWorking days between two dates, minus weekends and public holidays.
- Weeks Between Dates CalculatorWeeks and days between two dates, plus ISO week numbers.
- Hours Between Times CalculatorHours worked between two times, with breaks, overnight shifts and decimal hours.
- Age CalculatorExact age in years, months and days, plus your next birthday.
- All date & time calculatorsSee every calculator and which one to use.