Edited to clear up the info, as Korean age can be confusing: The above is correct. When you are born, you're 1. You gain a year when New Year's passes. To come up with your Korean age, add 2 if your birthday hasn't passed, add 1 if it has. The law follows your actual age. Korean age does not really affect your legal rights or privileges. If you are born early in the year and entered school earlier than others born in your year, you might be considered a year older, depending on who you're with (however, young children entering school now enter with others born in their calendar year). Your Eastern astrological sign still follows the Lunar calendar (if you are asked for your "띠"). Modern society tends to follow the "western" calendar, but many traditions still tend to follow the Lunar calendar. There's a mix. This was what I meant. My previous posting was just what I learned from my time there. Sorry if it caused confusion.

You are 1 when you are born and then everyone ages at the same time when a new year comes along. You can be 2 when you are just 1 day old.

They start with 1, so it's 'one up' compared to our system. You have to be '19' to watch porn in Korea, I think. And if you are born, you are already '1'.