Age Calculator
Calculate completed age in years between a birth date and any comparison date.
What this answers:
- How many full years old is someone, as of a given date?
A February 29 birth date is treated as occurring on February 28 in a non-leap comparison year — one explicitly stated convention, not the only one in use.
Completed age
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How it's calculated
Completed years = the calendar-year difference, minus one if the birthday hasn't occurred yet as of the comparison date.
Worked example
Born March 10, 1962, as of January 1, 2026: the calendar-year difference is 64, but March 10 hasn't occurred yet in 2026, so the completed age is 63 years.
Where this comes up in practice
Computing exact completed age "as of" a specific date, rather than today, comes up whenever a form or workflow needs age at a past or future reference point — for example, age as of a program enrollment date, or age as of a plan year's start. It's also a quick way to work out exact age around a birthday-linked threshold, such as turning 65 (the age most people become eligible for Medicare) — though actual eligibility and enrollment timing should always be confirmed at medicare.gov, not inferred from this calculation alone.
Age Calculator: Frequently Asked Questions
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