How it works
- 1Choose Age or Calendar Days mode.
- 2Enter the relevant date or dates.
- 3Calculate exact age, day difference, or a date shifted by a chosen number of calendar days.
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BROWSER · Calendar Date / JavaScript
Age & Calendar Day Calculator
Calculate exact age in years, months and days, count calendar days between two dates, or add and subtract days from any date.
✓ Runs locally in your browser✓ Calendar-aware date arithmetic✓ No account required
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About this tool
Age & Calendar Day Calculator performs calendar-aware date arithmetic locally in your browser: exact age, elapsed and inclusive calendar-day counts, and date addition or subtraction.
Common uses
age calculatorcalculate my agehow old am iage from date of birth
Frequently asked questions
What is the difference between elapsed days and inclusive calendar days?
Elapsed days is the number of 24-hour calendar boundaries between the dates. Inclusive calendar days counts both the start and end dates; for example, August 1 through August 2 is 1 elapsed day but 2 inclusive calendar days.
Does the age calculator account for leap years and different month lengths?
Yes. Age is calculated with calendar-aware year, month and day arithmetic rather than assuming a fixed number of days per month or year.
Can I add or subtract calendar days from a date?
Yes. Calendar Days mode can move a date forward or backward by an exact integer number of calendar days.