Pick a start date, choose add or subtract, then enter a number of days, weeks, months, years or working days. You get the new date, its weekday and its week number.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Add or subtract days from a date works
The calculator works in UTC, so clocks changing for daylight saving never shift a result by a day.
- Days and weeks: the date moves by that many days, or by seven times as many for weeks.
- Months and years: the month or year changes and the day of the month stays the same. If that day does not exist (31 January plus one month), the result is the last day of the shorter month.
- Working days: the date moves forward or back one day at a time, skipping Saturdays and Sundays. The start date is not counted, so one working day after a Friday is the Monday.
The result also shows the number of calendar days between the dates, the ISO 8601 week number (weeks start on Monday and week 1 contains the first Thursday) and the day of the year. Years from 1 to 9999 are supported. Bank holidays are not removed from working-day results, so for those use the working days calculator.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Start date | 2026-10-05 |
| Direction | Add |
| Amount | 90 |
| Unit | Days |
Date after adding: Sunday, 3 January 2027
| Start date | Monday, 5 October 2026 |
|---|---|
| Result | Sunday, 3 January 2027 |
| Calendar days between | 90 (12.9 weeks) |
| ISO week number | Week 53 of 2026 |
| Day of the year | 3 |
Tips and common mistakes
Check whether the deadline you are working to counts the start day: many contracts and notices do not, which is how this calculator works. For payment terms, notice periods or legal time limits, read the wording and use a date from the documents rather than a guess. If bank holidays matter, use the working days calculator. For a difference between two dates, use the days between dates calculator instead.
Frequently asked questions
What is 90 days from today?
Enter today’s date, choose Add and enter 90 days. The calculator shows the date, its weekday and its week number.
What does adding one month to 31 January give?
It gives the last day of February, as that month has no 31st. Month and year steps keep the day of the month wherever possible.
Are working days affected by bank holidays?
Not here: only Saturdays and Sundays are skipped. Use the working days and bank holidays calculator to remove public holidays.