Date & Time
Age, duration & timezone calculators
Chronological Age Calculator
Work out an exact chronological age — the whole years, months and days between a birth date and a chosen date — for school-entry cut-offs, developmental and clinical assessments, eligibility and forms. Enter the date of birth and the as-of date and the calculator shows the age as years, months and days, plus the total days and weeks lived and a countdown to the next birthday. For example, a birth date of 24 June 1990 as of 24 June 2026 is exactly 36 years, 0 months and 0 days — a birthday — which is 13,149 total days including leap days. The breakdown uses calendar-aware borrowing (the correct length of each preceding month, with leap-year handling), not a rough divide-by-365, and every calculation runs on UTC midnights so a day is always a full calendar day, even across a daylight-saving change. Everything is computed in your browser, and the two dates can be entered in either order.
Age = whole years, then months, then residual days (calendar-aware month-length borrow)
- Born 24 Jun 1990, as of 24 Jun 2026 = 36 years 0 months 0 days = 13,149 total days
- Also shown: total weeks lived and a next-birthday countdown
Frequently asked questions
What is chronological age?
Chronological age is the exact time a person has been alive, expressed as whole years, months and days from the birth date to a given date. It is the age used for school-entry cut-offs and for developmental or clinical assessments, where the precise years-months-days figure matters.
How do I calculate chronological age in years, months and days?
Take the whole years between the birth date and the as-of date, then the whole months, then the leftover days, borrowing the length of the preceding month when the day-of-month has not yet been reached. This calculator does that calendar-aware borrowing for you and also shows the total days and weeks lived.