Add or subtract days
Find the date a number of days, weeks, months or years before or after any date.
How to add or subtract days from a date
Start from a date and move it forward or back by any number of years, months, weeks or days. It answers "what is 90 days from today", "when is 6 weeks before the wedding" and "what date is 18 months after the lease started".
Step by step
- Enter the Start date in any format, or pick it from the calendar. It starts on today's date.
- Choose Add or Subtract.
- Enter how many years, months, weeks and days to move. You can combine them, for example 1 month and 15 days.
- Tick Repeat to get a series: 12 repeats of 1 month gives the next twelve monthly dates.
- Press Calculate new date. The result shows the new date and a calendar of the period, and has its own web address.
Worked examples
- A 90 day deadline: October 19, 2026 plus 90 days is Sunday, January 17, 2027.
- Month ends: January 31, 2027 plus 1 month is February 28, 2027, because February has no 31st. In a leap year it would be February 29.
- A payment schedule: January 31, 2024 plus 1 month, repeated 3 times, gives February 29, March 29 and April 29, 2024. Each date starts from the previous result.
Common uses
- Deadlines from today. "You have 90 days to respond" or "valid for 180 days": start from today, add the days, and the result is the last day.
- Due dates and expiry dates. A warranty of 2 years, a passport valid for 10 years, a subscription that renews every 3 months: add the term to the start date.
- Planning backwards. If the venue needs the final numbers 6 weeks before the event, subtract 6 weeks from the event date.
- Schedules. Tick Repeat to list a series of dates, such as 12 monthly payments from the first due date or 26 fortnightly paydays.
Reading the result
The result shows the start date, what was added or subtracted, and the new date written out with its day of the week. When Repeat is on, every date in the series is listed with its ISO form, ready to paste into a spreadsheet. The calendars mark the start date in blue and the result in yellow. "New calculation from" the result lets you chain steps, for example 30 days and then 3 business days, by starting the next calculation from the date you just found.
Rules this tool follows
- Order of operations. Years and months are applied first, then weeks, then days.
- Month ends clamp. If the result would fall on a day that does not exist, such as April 31, it moves back to the last day of that month.
- Every day counts. Weekends and holidays are included. To skip them, use Add or subtract business days.
Questions people ask
Why did adding a month land on a different day of the month?
Because the target month is shorter. January 31 plus one month becomes February 28 or 29. The tool never rolls over into the following month.
Can I list several dates at once?
Yes. Tick Repeat and set how many you want, up to 100. Each one is one interval after the previous one, which suits payment schedules, medication cycles and recurring reminders.
How do I continue from the result?
Under the result, press "New calculation from" the result date. It becomes the new start date with the same amounts.
How far can I go?
Years 0001 to 9999. If a result would fall outside that range the tool says so.
Is my date sent anywhere?
No. All date math runs in your browser.