AGE CALCULATOR

Saying someone is 34.7 years old is mathematically tidy but practically useless, because months have different lengths. The calendar method used here counts full years first, then full months, then leftover days — the same way a doctor, a passport office, or a school registrar does it. That's why your age in days is never simply your age in years times 365.

About one in 1,461 people is born on February 29 and has no birthday in common years. There's no single global rule for what happens then: many U.S. states treat March 1 as the legal birthday for things like driver's licenses, while other jurisdictions use February 28. This calculator follows the common convention of rolling to March 1 in non-leap years, so a leap-day baby still ages exactly one year, every year.

The "age zero at birth" system feels universal but isn't. In the traditional East Asian reckoning still used informally in parts of the region, a newborn starts at one and everyone gains a year at New Year — so a baby born in December could be considered two years old within weeks. South Korea officially moved to the international system in 2023. If a form ever asks for your "international age," this is the number it wants.

Knowing your own age is easy. Remembering your father-in-law's birthday is the hard part. Our free special-day reminder tool builds a recurring event straight into your own calendar — no account, no email, and nothing stored on our servers.