How to Calculate Age Manually — Step by Step
Learn the exact method for working out age from a date of birth, with worked examples and common pitfalls.
Chronological Age vs Biological Age
Your calendar age and your body's age are not always the same. Here is what the difference means.
The Korean Age System Explained
Why Koreans were "one or two years older" — and what changed when South Korea switched in 2023.
Leap Year Birthdays: When Do February 29 Babies Celebrate?
The rules, laws and fun traditions around the rarest birthday of all.
Legal Ages Around the World
Voting, driving, drinking and retirement ages compared country by country.
How Many Days Old Am I?
Days-alive milestones — including your 10,000th day — and how to calculate yours.