Date Calculator

Enter a start date and an amount to add or subtract to calculate the resulting date.

How to Use the Date Calculator

Choose the unit from the dropdown — days, weeks, months, or years all shift the date differently — before deciding whether to add or subtract from the start date.

Adding a month to a date sounds simple until you try it on January 31st — there's no February 31st, so the calendar has to make a decision about what happens. This Date Calculator adds or subtracts days, weeks, months, or years from any starting date, using the browser's native date handling rather than a hand-rolled calendar table, which is exactly what makes it get leap years and short months right without any special-case code.

Months and years shift the calendar position directly (so adding a month to January 31 lands on the last valid day of February, not 3 days into March); days and weeks just add raw time. Subtracting works identically in reverse.