A date calculator adds or subtracts a specified number of days, weeks, months or years from a starting date to find a resulting date. It is useful for calculating deadlines, due dates, expiry dates, notice periods and any situation where you need to find a date a certain amount of time before or after a known date.

1. Select a start date.
2. Enter the number of days, weeks, months or years.
3. Select the unit and whether to add or subtract.
4. Click Calculate.

Start: 15 March 2025, add 90 days → 13 June 2025 (Saturday)
Start: 1 January 2025, add 6 months → 1 July 2025 (Tuesday)

When adding months, the calculator uses calendar months. Adding 1 month to January 31 gives the last day of February (28 or 29). Adding years follows the same rule — adding 1 year to February 29 in a leap year gives February 28 in a non-leap year.

• Confusing calendar months with 30-day periods — use "days" if you need exactly 30 days.
• Forgetting that month-end dates can shift when adding months to dates near the end of a month.

What date is 90 days from today?

Enter today's date as the start, enter 90 as the amount, select "days" and "add", then click Calculate.

Can I calculate a date in the past?

Yes. Select "subtract" to go back in time from the start date.