Date Calculator

How the Calculation Works

This calculator starts from your chosen date and moves forward or backward by a calendar interval using standard Gregorian calendar arithmetic. Adding or subtracting days or weeks is simple day-count math (a week is always treated as 7 days). Adding or subtracting months or years uses calendar-aware rollover: the day-of-month is kept the same where possible, and if the target month is shorter than the start day (for example, adding one month to January 31), the date is clamped to the last valid day of that month rather than overflowing into the next one — the same convention used by spreadsheet software and most date libraries.

A Common Misconception About "Adding a Month"

Adding one month is not the same as adding 30 days. Months vary from 28 to 31 days, so "3 months from now" and "90 days from now" usually land on different dates. If you need an exact day-count offset rather than a calendar-unit offset, choose Days as the unit here. Leap years are handled automatically: February 29 only appears in years divisible by 4 (excluding century years not divisible by 400), and the calculator relies on the browser's native date engine to apply that rule correctly.

Have Two Dates Instead of One?

This tool answers "what date is N days/weeks/months/years from this date?" If you already know both a start and an end date and want to find the number of days between them instead, use the day counter. For adding up hours and minutes rather than calendar dates, see the time calculator.