The day starts at zero, not 12. 12 is “Noon” ie halfway through the day. The clock starts at 12 because it’s more practical than inscribing 24 divisions in a circle. And the 6 doesn’t “mean 30”, it’s simply the hour marking at the bottom of the circle. Finally, the 12 hour clock was invented after the 24 hour day, not the other way around.

And inb4 “I bet you’re fun at parties”. I’m all for “this logic is ridiculous” jabs, but this is just misrepresenting everything to make it sound stupid. Everything sounds stupid when you purposefully get it wrong.