Chronological Age Calculator


This Chronological Age Calculator finds a person’s age or interval between two dates of Gregorian calendar.


Birth Date

Test Date

Chronological Age


Definition of Chronological Age

Your chronological age is the amount of time that has passed from your birth to the given test date. It’s your age based on the calendar year and expressed in terms of years, months and days.

Your chronological age determines your eligibility for school, for work, or for retirement. It’s also an important risk factor for chronic diseases, mortality, and some impairments to bodily functions, such as hearing and memory.

Chronological age differs from biological age (also known as physiological or functional age). While chronological age is the number of years a person has actually lived, biological age refers to how old a person appears to be.

Biological age depends on a person’s genetics and many lifestyle factors, including diet, exercise, stress and sleeping habits. It also depends on having bad habits such as smoking. As a result you may not end up having the same biological age as your chronological age.

How to Calculate Chronological Age

Our Chronological Age Calculator finds your chronological age by subtracting your date of birth from the test date. Subtracting dates is similar to subtracting numbers. The only difference is that when you subtract months, you only use numbers 1-12 and for days, you only use numbers 1-31. You also need to take into account how many days each month contains and not forget about leap years.

As a result, finding the chronological age is not so easy as it may seems. Let’s consider an example. A person’s date of birth was September 30, 1995. The person checked his chronological age on June 13, 2020.

First, start by subtracting the days. But the number of days for the test date (13) is less than the number of days for the date of birth (30). Therefore, we need to borrow 31 days (1 whole month) from the numerical value of the previous month of May. It means that for the test day, the number of days would be 44 (13+31) while the number of months would be 5 (the month of May). Then subtracting 30 from 44 we will get 14 days.

Now, we have to subtract months: 9 (September) from 5 (May). Again we need to borrow the whole year (12 months) from the test year. As the result we have to subtract 9 from 17 (5+12) and we will get 8 (months).

And finally we have to subtract years. The year of birth 1995 we subtract from 2019 (the test year minus 1 borrowed) and have 24 years as the result. So the person’s chronological age is 24 years 8 months and 14 days.

This very result we can instantly obtain using our Chronological Age Calculator without resorting to tedious manual calculations.


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