Why an exact age sometimes matters
Pension paperwork, medical forms, school enrolment cut-offs, child-passport renewals and many legal documents in Canada ask for age as of a specific date — not just today. Knowing your age in years and months on a particular date can save a phone call to a benefits office.
How the maths work
We start with the difference in calendar years between the two dates, then walk back one calendar month at a time if the target day is earlier than the birth day. The algorithm respects the actual length of each calendar month, including leap years (Feb 29).
Birthdays at the boundary
If you were born on 29 February (leap day), you only get a “true” birthday every four years. The calculator handles this by treating 29 February in non-leap years as 28 February for the purpose of computing whole years.