Subtracting the two year numbers is not enough to calculate age. You must also determine whether the relevant birthday has occurred by the target date.
Calendar-age method
Start with the difference between the year numbers. If the target month and day come before the birth month and day, subtract one year. For a years-months-days result, count complete months after the last birthday and then remaining days.
Example before a birthday
Someone born October 20, 2000 is 25 on August 3, 2026, not 26, because the October birthday has not occurred.
Age on a specific date
Applications and eligibility rules often specify a closing date. Use that date as the target rather than today's date and retain evidence of the applicable policy wording.
Leap-day birthdays
Calendar arithmetic can measure elapsed time from February 29, but a legal rule may recognize a birthday on February 28 or March 1 in a non-leap year. Check the governing jurisdiction when eligibility or legal age matters.
Age versus elapsed days
Calendar age answers how many birthdays or complete calendar units have passed. Elapsed days counts every day in the interval, including leap days. Both can be correct while serving different purposes.