How to Calculate Age: Chronological Methods and Leap Years

Last updated: 2026-09-11 • Editorial Staff

Calculating exact age appears simple on the surface, but accounting for leap years, differing month lengths, and specific target dates requires systematic date math.

Date Arithmetic Principles

To determine chronological age in years, months, and days: compare the target date against the birth date.

If the target day is less than the birth day, borrow the total days from the preceding month.

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