In the UK it's not that it's used scarcely, it's that the expression is usually written as "9-5".

Hmm, yeah... In Greece we use it interchangeably with the 12-hour time, but whenever my brain sees 17, it just translates it to "5", so the expression made sense. Then again, I skipped that part in the article and only saw it in the comments, so I may have already been primed for it.

We use the 24 hour time here in Portugal (in every digital clock, written information, etc), but it also threw me off. 9-5 is a common linguistic expression, while 9-17 reads "nine to seventeen" to me. Maybe "9-17h" would work better.

As someone from the US that uses a 24 hour clock everywhere, I've gotten many questions and weird looks.