Since you were talking about Korean age, they used to start with the day you are born as the first year. So in your 1st birthday, you'll be starting your second year. But in 2023, they officially announced that Korea will follow international age from now on. Also fun fact since they showed a clip from 218 bro's, Vernon and DK were born in the same day Feb 18th (same as J hope), but different years. And Joshua shares the same birthday as V (Dec 30, 1995)