Under the age system most commonly used in South Koreans’ everyday life, people are deemed to be a year old at birth and a year is added every Jan. 1.

South Korea switches to the international way of counting age, starting from 0 at birth and adding 1 on every birthday, instead of starting from 1 at birth and adding 1 on Jan 1st every year.

There is yet another system used in South Korea for conscription, school entrance and calculating the legal age to drink alcohol and smoke - start from 0 at birth and add 1 on every Jan 1st. This one’s still in effect though.