SASQuick Tools

Time & dates

Age Calculator

Find an exact age in completed years, months, and days — on today's date or any date you choose.

  1. Enter the date of birth.
  2. Optionally change the “age on” date (defaults to today).
  3. Read the age and total days lived.
Enter values to see the result.

How it works

The calculator counts how many whole months have passed between the date of birth and the date you choose. Twelve whole months make a year, and the leftover months are shown separately. The remaining days are counted from the last monthly anniversary of the birth date.

Real calendar dates are used, so leap years and months of different lengths are handled automatically. When a birth date falls on a day that a month doesn't have, such as the 31st, the anniversary is counted on the last day of that month. Total days lived are also shown, which is useful for forms and milestones.

Because the calculation follows the real calendar rather than an average month length, the answer matches the way people normally count birthdays. That makes it suitable for checking eligibility dates, school entry ages, insurance forms and retirement planning, where being one day out can matter. Your dates are worked out in your browser and are never stored or sent anywhere.

Formula

Count whole months from birth date to the target date

Years = whole months ÷ 12, Months = remainder

Days = days since the last monthly anniversary

Worked examples

Born 2000-02-29, on 2023-03-01: 23 years, 0 months, 1 day.

Today's age

Born 14 May 1990, on 27 October 2026: 36 years, 5 months, 13 days.

Age on a deadline

A child born 1 September 2020 is 6 years, 0 months, 0 days on 1 September 2026 — exactly the cut-off age.

Leap-year birthday

Born 29 February 2000, on 1 March 2023: 23 years, 0 months, 1 day.

Understanding the result

When a birthday falls on a day a month doesn't have (like the 31st or 29 February), the anniversary is counted on that month's last day. Leap years are handled by the real calendar.

Common mistakes

  • Subtracting birth year from current year, which is wrong for anyone whose birthday hasn't arrived yet this year.
  • Mixing day and month order when entering dates from another country.
  • Using today's date when a form asks for age on a specific date.
  • Assuming every month has 30 days when counting days by hand.

When to use it

  • Filling in forms that ask for exact age.
  • Checking eligibility for school, sport, or retirement cut-off dates.
  • Working out a baby's age in months.
  • Counting days lived for a milestone celebration.

FAQs

When does someone born on 29 February have a birthday?
In non-leap years this calculator counts the birthday on 28 February. Legal conventions vary by country.
Is my birth date stored?
No. It's calculated in your browser and never saved or sent anywhere.
Can I calculate age on a past or future date?
Yes. Change the “age on” date to any date after the birth date.
Why is the day count different from my own count?
Days are counted from the most recent monthly anniversary, not from the start of the month.
Does time of birth matter?
No. The calculator works in whole calendar days.

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