Most people assume that age is calculated the same way everywhere in the world. In reality, different cultures have very different systems — and some may surprise you considerably.
In most Western countries including the UK, USA, Australia and Europe, age is counted from the moment of birth. You are zero years old until your first birthday, when you turn one. This is the most widely used system internationally.
In traditional Korean, Chinese and Vietnamese cultures, a baby is considered to be one year old at birth. The time spent in the womb counts as the first year of life. In South Korea, this traditional system was officially used in official contexts until 2023, when the government standardised the Western system for legal purposes.
Japan historically used a system called kazoedoshi, where everyone became one year older on New Year's Day regardless of their actual birthday. This meant two people born on December 31st and January 1st could be the same age for most of the year but differ by two kazoedoshi years immediately after New Year. This system is now rarely used in modern Japan.
Our Age Calculator uses the internationally recognised Western system, giving you the most widely accepted and legally accurate age for official use anywhere in the world.