Eh, the implication has always been that it's a Christmas calendar where you open one door per day until it's Christmas eve - just with code riddles instead of chocolate.

> one door per day until it's Christmas eve

That would be 24.

You also open one on Christmas. Some people consider Christmas more important than Christmas eve.

https://www.hallmark.com/house-and-home/figurines/precious-m...

That really depends on which country you're in.