In Germany it‘s even more confusing. In the West people say „Viertel nach Neun“ and “Viertel vor Zehn” which is pretty much „quarter past nine“ and “quarter to ten”, while in Eastern Germany people say “Viertel Zehn” and “Dreiviertel Zehn” which rather means “quarter of ten” and “three quarters of ten”. Even though they are meaning exactly the same times.
My English-speaking father with German heritage said both “quarter to ten” for 9:45 and “quarter of ten” for 10:15. He’s the only person I’ve heard say “quarter of ten”. Now I know that could be from his German heritage even though he never learned German.