Date Calculator
Add or subtract days, weeks, months, and years from any date. Find the date after N days or the number of days between dates.
Add / Subtract from Date
Days Between Two Dates
About this calculator
The Date Calculator does the two jobs people actually need: add or subtract days, weeks, months or years from a date, and count the days between two dates. It also tells you the weekday of the answer.
Use it for deadlines (what is the date 90 days after an invoice?), notice periods, loan and visa dates, medicine courses and project plans. Months and years are added on the calendar, not as 30 or 365 days, so adding one month to 31 January gives the end of February.
How to use it
- Choose the Start Date.
- Choose Add or Subtract, enter a number and pick days, weeks, months or years.
- Press Calculate to see the resulting date and weekday.
- For the interval between two dates, fill in both dates in the second box and press Calculate.
How dates are added
For days and weeks, the tool adds Number × 1 or 7 days. For months and years it moves the calendar month or year, which keeps the day of the month where possible. Days between two dates is |Date 2 − Date 1|. The business-day figure in the second box is an estimate of days × 5 ÷ 7 that does not remove public holidays.
Worked example
90 days after 8 November 2026
| Result | 6 February 2027 |
| Weekday | Saturday |
| Days from start | 90 |
If a payment term of 90 days falls on a Saturday, check whether your contract moves it to the next working day.
Tips and common mistakes
- Months are not 30 days. Adding 3 months to 30 November gives 28 February, not 28 February plus a day.
- For contracts, check whether the start day counts as day one.
- The business-day estimate ignores holidays. Use the Working Days Calculator for an exact count.
- Use subtract to work backwards from a deadline, such as 6 weeks before an event.
- Dates are shown in day-month-year format.
Frequently asked questions
How do I add days to a date?
Enter the start date, choose Add, enter the number of days and press Calculate.
How do I find a date 90 days from today?
Leave the start date as today and add 90 days.
Does adding a month use 30 days?
No, it moves to the same day of the next calendar month where possible.
How many days are there between two dates?
Fill in both dates in the second box. The tool shows days, weeks and an approximate number of months.
Does it count business days?
Only as an estimate. The Working Days Calculator gives an exact count excluding weekends.
Can I subtract years?
Yes, choose Subtract and the year unit.