A few years ago, iirc, the Korean government instructed people to stop using the traditional system and to use the international system instead. Has that had much of an effect in practice, or are people largely ignoring it? Or do you think it's something that younger generations will pick up more over time while older people continue using the traditional system? (This last option being sort of what happened in Australia when we transitioned to metric through the '70s.)

Also, what happens to someone born on 1 January? Are they born du sal, and thus the youngest of their sal, or born han sal and remain han sal for a whole year?