The Korean approach does not account for preconception well at all. It counts the number of calendar years a person has been present for postpartum.
A person's Korean age starts at 1 sal, and increments at New Years. A baby could be born on December and be 2 sal by January. A baby born in January would be 1 sal until next year, and be considered 1 sal younger than the December baby, even though they were only born 1 month apart. Everyone born in the same calendar year is in the same age cohort.
A person's Korean age starts at 1 sal, and increments at New Years. A baby could be born on December and be 2 sal by January. A baby born in January would be 1 sal until next year, and be considered 1 sal younger than the December baby, even though they were only born 1 month apart. Everyone born in the same calendar year is in the same age cohort.