Age Calculator

Exact age uses calendar arithmetic: count complete years (birthday hasn't occurred yet this year → subtract 1), then count remaining months, then remaining days. It's not simple division by 365 because months have different lengths and leap years add complexity. Example: born March 31 → age at Feb 28 is "not yet the birthday month" = 1 day short of the next year. Most legal systems use the calendar day interpretation.

Age calculation varies by country and context: Most countries count completed years (you turn 18 on your 18th birthday). East Asian traditional age: add 1 at birth, increment at each lunar new year — so a baby born in December could be "2" by February. Korean age system: born = 1 year old, +1 each January 1st. South Korea moved to Western age for official purposes in 2023. Legal age for various purposes (voting, driving, drinking) uses the calendar birthday.

People born on February 29 (leap day) only have a birthday in leap years (divisible by 4, except centuries unless divisible by 400). In non-leap years, different countries treat it differently: some celebrate Feb 28, others March 1. Legal age: most countries use Feb 28 in non-leap years. Statistically, the chance of being born on Feb 29 is 1 in 1,461 (roughly 1 in 4 years × 365 days). About 5 million people worldwide have Feb 29 birthdays.

Age in days = (current date − birth date) in days. Accounting for leap years: a 30-year-old has lived through approximately 7-8 leap years, so roughly 30×365 + 7 ≈ 10,957 days. Notable milestones: 10,000 days ≈ 27 years 4 months, 20,000 days ≈ 54 years 9 months. In seconds: a 30-year-old = approximately 946,728,000 seconds. One million seconds ≈ 11.5 days. One billion seconds ≈ 31.7 years.

A golden birthday (or lucky birthday) is when your age matches your birth date. If you were born on the 15th, your golden birthday is when you turn 15. Born on the 31st → golden birthday at 31. This concept was popularized in the US in the 1950s-60s. Other special age milestones: platinum birthday = 100 years, diamond birthday = 75 years, golden wedding anniversary = 50 years of marriage.