Add Days to a Date
Enter a date and the number of days to add or subtract. You get the new date and the weekday straight away.
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The formula
New date = start date + number of days (the start date is day 0).
What it does
Pick "Add to a date" or "Subtract from a date", enter a start date and the amounts. You can mix units, for example 1 year, 2 months and 10 days.
Choose "Days between two dates" if you want the gap between two dates instead.
How months and month ends are handled
Months and years are applied first, then weeks and days. If the start day does not exist in the target month, we use the last day of that month. So 31 January plus 1 month is 28 February, not 3 March.
Worked examples
| Start | Change | Result |
|---|---|---|
| 3 Oct 2026 | + 90 days | 1 Jan 2027 |
| 31 Jan 2026 | + 1 month | 28 Feb 2026 |
| 1 Mar 2026 | - 1 day | 28 Feb 2026 |
How to add days to a date
The start date is day zero, so adding 30 days to 3 October gives 2 November. The calculator handles the different month lengths and leap years for you.
To count backwards, switch to "Subtract from a date". That is useful for finding when something started, such as the date 90 days before an expiry.
Common targets
| From 3 Oct 2026 | Date |
|---|---|
| + 7 days | 10 Oct 2026 |
| + 30 days | 2 Nov 2026 |
| + 60 days | 2 Dec 2026 |
| + 90 days | 1 Jan 2027 |
| + 180 days | 1 Apr 2027 |
Calendar days or working days?
This tool counts every calendar day, weekends included. If a contract says "30 working days", use the business days calculator instead, because 30 working days is about six weeks.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Add to a date; Start date: 2026-10-03; Days: 30 | Result: Monday, November 2, 2026 |
| Add to a date; Start date: 2026-10-03; Days: 90 | Result: Friday, January 1, 2027 |
| Subtract from a date; Start date: 2026-10-03; Days: 45 | Result: Wednesday, August 19, 2026 |
| Add to a date; Start date: 2026-12-20; Days: 14 | Result: Sunday, January 3, 2027 |
Add Days to a Date: frequently asked questions
What is 30 days from today?
Enter today in the date box and 30 in the days box. The result is the date 30 calendar days ahead.
Is the start day counted?
No. The start day is day zero, so day 1 is the following day.
Does the calculator count the start date?
No. Adding 1 day to 1 March gives 2 March. The start date itself is day zero.
What happens when I add a month to the 31st?
We move to the last day of the shorter month. Adding one month to 31 January gives 28 February (29 in a leap year), which matches how most calendars and spreadsheets behave.
Does it take leap years into account?
Yes. Calculations use real calendar dates, including leap days and the different lengths of months.
Is what I enter in this calculator saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Last reviewed: October 3, 2026