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Date Calculator

Add or subtract days, or find the difference between two dates.

How to use Date Calculator

  1. Choose between finding the days between two dates, or adding and subtracting time from a base date.
  2. For date difference: pick the start date and end date.
  3. For add/subtract: pick the base date, enter years, months, weeks and days, then choose Add or Subtract.

About Date Calculator

Calculations with dates are tricky because months have different lengths and leap years add an extra day every four years. This calculator uses calendar-aware arithmetic so, for example, adding "one month" to 31 January gives the last day of February, not a date in March.

All math runs in your browser using your local time zone. Dates are compared at calendar-day level, not time-of-day level.

Features

  • Difference mode: years, months, days, plus total days, weeks and hours
  • Add/subtract mode with years, months, weeks and days in a single operation
  • Choice of Add or Subtract
  • Uses real calendar rules, including leap years

Frequently asked questions

Why does adding one month sometimes skip a month?

It keeps the day number when possible, clamping to the last valid day of the target month. 31 Jan + 1 month = 28/29 Feb, not 3 Mar.

Does it consider my time zone?

Date values are interpreted in your browser local time zone. Daylight saving transitions do not affect the calendar-day result.

Can I work out someone age with this?

The Age Calculator is tuned for that specific question with extra fields like next birthday, but the difference mode here will also give you the calendar age.

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