Date Calculator (Add/Subtract)

Enter your start date, select 'Add' as the operation, type the number of days you want to add in the Days field, and the calculator will display the resulting date. You can also combine years, months, and weeks in the same calculation.

When adding or subtracting months would result in an invalid date — for example, adding one month to January 31 — the calculator adjusts to the last valid day of the target month. So January 31 + 1 month = February 28 (or 29 in a leap year).

Adding weeks is equivalent to adding multiples of 7 days. For example, adding 2 weeks gives the same result as adding 14 days. Both fields can be used at the same time and the calculator sums them all before computing the result.

This tool adds or subtracts a duration to a known date. If you want to find the number of days between two specific dates, use a Date Difference Calculator instead, which calculates the span between two calendar dates.

Yes. The calculation uses standard JavaScript Date logic, which correctly handles leap years. Adding one year to February 29 in a leap year will land on February 28 in a non-leap year.

Total Days Changed shows the net number of calendar days between your start date and the resulting date. It accounts for the actual number of days in each month crossed during the calculation, so it may differ from a simple multiplication of your inputs.

Yes — all four duration fields work together. The calculator first adds or subtracts years and months to the start date, then adds or subtracts the combined total of weeks and days. Leave any field at 0 to exclude it.

This calculator uses the Gregorian calendar, which is the internationally accepted civil calendar today. It accounts for standard month lengths (28–31 days) and the leap year rule of adding a day to February every four years, with century-year exceptions.