What it does
A multi-purpose date toolkit that runs entirely in your browser:
- Difference between two dates — get the exact number of years, months, days (and total days/weeks/hours) between two dates.
- Add or subtract time from a date — add/remove a number of days, weeks, months, or years from a starting date.
- Age calculator — enter a birth date and get an exact age in years, months and days, plus fun facts like total days lived and next birthday countdown.
Try it
How it works
Difference between two dates
The tool computes the exact calendar difference (years, months, days) between the two dates by walking month-by-month/day-by-day rather than just dividing total milliseconds — this correctly handles varying month lengths and leap years. It also shows the total elapsed time in several units (total days, total weeks, total hours, total minutes) for convenience.
If the end date is earlier than the start date, the two are swapped automatically and a note is shown.
Add / subtract from a date
Starting from a base date, adds or subtracts a chosen amount of days, weeks, months, years, hours, or minutes. Adding/subtracting months or years uses calendar-aware arithmetic (via setMonth/ setFullYear), so e.g. adding 1 month to January 31st correctly lands on the last day of February rather than overflowing into March.
Age calculator
Computes an exact age in years/months/days as of now (or as of a custom date you provide), plus:
- Total days lived
- Total weeks lived
- Days remaining until the next birthday
- The day of the week the person was born on
Notes
- All calculations happen locally in your browser — no dates are ever sent anywhere.
- Calculations use your browser's local timezone. If you leave the time portion at
00:00, that's treated as midnight in your local timezone. - The "as of" field in Age mode defaults to the current date/time if left empty.