How age is calculated
Age is counted the standard Western way: you are 0 on the day you are born and gain a year on each birthday. The calculator subtracts the birth year from the current year, takes one year off if this year's birthday has not happened yet, then counts the remaining whole months and finally the days.
Worked example
Someone born on March 15, 1990 is 36 years, 6 months and 13 days old on September 28, 2026: 36 years to March 15, 2026, six months to September 15, 2026, and 13 more days. The calculator also shows the same span as a total number of months, weeks and days.
Leap years and February 29 birthdays
Leap years are handled automatically, so every day between the two dates is counted exactly. People born on February 29 usually celebrate on February 28 or March 1 in common years; the date on which they legally reach a given age depends on local law.
Other uses
Because the tool measures the time between any two dates, you can also use it for the age of a building, the length of employment, the time since a wedding or the exact age on a past or future date, such as the day of an exam or retirement. For plain day counts, use the days between dates calculator.