How do I calculate chronological age from birth date?

Subtract the birth date from the target date and normalize years, months, and days with borrowing rules.

What if month and day differences are negative?

Borrow from the previous month for days, and from the year for months.

Yes. Use the calculator with the same dates and compare final Y-M-D output.

This page focuses on one question: how to compute precise chronological age from date-of-birth data with minimal error risk.