How it works
Calendar age is calculated by advancing whole years and months from the birth date, then counting the remaining days. This avoids treating every month or year as the same length.
Using the result
Birthdays on leap day may be recognized on February 28 or March 1 in non-leap years depending on the context and local rule.
Important limitation
Use the target-date field to calculate age on a historical or future date rather than only today.