Summary
Calculate age on a specified date.
Calculation details
The as-of date must not precede the birth date. Leap days are handled as calendar dates.
Formula
Age is the completed calendar years, months, and days between birth and as-of dates.
Worked example
Worked example
The completed calendar age is 25 years.
How it works
Enter birth date and as-of date. Completed years, months, and days use UTC calendar arithmetic so leap days stay stable across time zones.
Frequently asked questions
Does the age calculator use my browser time zone?
Birth and as-of dates are treated as UTC calendar dates, so changing your device time zone does not rewrite the entered dates.
Why can age differ from what a form asks for?
Some forms count completed years only, or use local midnights. This tool reports years, months, and days between the two calendar dates you enter.
What if the as-of date is before the birth date?
The calculator rejects that combination. Use an as-of date on or after the birth date.