[firstcommentyo]

Welcome to MMXXII. About X centuries ago "we" imported the Hindu-Arabic numerals. I know, Latin numbers carry the myth of being more "safe" but really you should try the arabian numerals. They revolutionized math and eased reading text alongside. thumbs-up

[rossvor]

It's a convention to use roman numerals for centuries in some european countries. Parent poster probably just done it out of habit.

[puszczyk]

Thanks, I wasn’t aware it is not a “global” convention and wasn’t sure what does the parent make fun of.

One learns every day :) I will be more careful about this when writing centuries in English the next time.

Also this poster on quora have a detailed list https://www.quora.com/Why-do-we-write-century-numbers-with-I...