You say that in some regions of Germany (and also in Austria, I think). It's quite confusing for the rest of us. Just remember: "dreiviertel acht", which means "3/4 of the hour to get 8 o'clock".
7:15 Uhr is, for example, "viertel acht",
7:30 Uhr "halb acht" and
7:45 Uhr "drei viertel acht".
Not hard to remember, but still confusing if you are used to say "viertel nach sieben", "halb acht" and "viertel vor acht".