From what I understand, they've been using the 'normal' system for most legal things since the 60s, and that was just how they socially talked about age, until it was abandoned in 2023.

The old system also added a year on New years, not on your birthday. Meaning a baby born 2 days ago would be 2 years old if they were born on December 31. Apparently, laws do still keep that standard for some age based regulations, like school, drinking age, voting age, and draft. Which kind of makes sense; everyone born in X year gains those things at the same time. A less arbitrary cut off date for schools, no awkward math whe checking IDs, just born in '04, you're good.'

Still seems confusing having 3 ages in different contexts though.

It was also counted from the beginning of the year https://en.wikipedia.org/wiki/East_Asian_age_reckoning but they oficially switched in 2023

Aren't they getting one year every 1 January or something like that?

There is actually one problem with counting age from birth: premature babies are behind on everything! Of course we could correct that by saying that they were minus three months old when born (or however early they are).

That's it, we'll have to get rid of democracy now, there's too many flaws.