Exact age in years, months, and days on any date, with totals, your birth weekday, and the next birthday countdown.
| Born on a | – |
| Next birthday | – |
| Days until next birthday | – |
| Age at next birthday | – |
| Last birthday | – |
| Age in decimal years | – |
| Step | Working | Result |
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The Age Calculator turns a birth date into an exact age on any date you choose, today by default. It reports years, months, and days the way a person would count them on a calendar, then adds totals in months, weeks, days, and hours, the day of the week you were born, and the date and countdown for your next birthday. It handles month-end and leap-day birthdays correctly, so someone born on February 29 sees a sensible age on February 28 and March 1 of a non-leap year. Useful for forms that ask for age on a specific date, eligibility checks, and simple curiosity.
Both dates are read as local calendar dates at midnight. The calculator finds the last birthday anniversary on or before the target date (whole years), then the last monthly anniversary after that (whole months), then counts the leftover days. Anniversaries that land on a day the month does not have are clamped to the month's last day, which keeps month-end cases correct: Jan 31 to Mar 1 is 1 month 1 day, and Feb 29 to the next Feb 28 is 11 months 30 days. Total days come from Math.round((on - birth) / 86,400,000) so a daylight-saving change never produces an off-by-one, and total months are years x 12 + months.
The birthday anniversary falls on Feb 28 in a non-leap year in this calculator, so a person born 2000-02-29 is 23 years 11 months 30 days on 2024-02-28, exactly 24 on 2024-02-29, and 24 years 0 months 1 day on 2024-03-01. Some jurisdictions treat March 1 as the legal birthday instead.
Months have 28 to 31 days, so an age of 36 years 2 months 28 days cannot be derived by dividing total days by 30.44. The calendar method counts whole calendar months first, then leftover days, which is why the two views differ slightly.
Yes. Change the 'Age on date' field to any date. Ages on dates before the birth date are shown as an error rather than a negative number. This is useful for eligibility dates, school-entry cutoffs, and retirement or pension milestones.
It is total days x 24, which ignores the time of day you were born and the one-hour shifts at daylight-saving transitions. For a precise figure to the hour you would need your birth time and the time zone history of your birthplace.
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