I am a German language beginner. I understand that, in principle, the time 17:45 could be referred to (informally, unofficially) as either "Viertel vor sechs" ("a quarter to six") or "dreiviertel sechs" ("three quarters [...] six") and that the latter is less common and only used in some parts of Germany and Austria.
How common in practice is this latter (and to an English native speaker, very confusing) form and in which parts of the German-speaking world can I expect to encounter it?
By extension, does "viertel sechs" (without the "vor") mean 17:15 in these parts of the world?