As a British person who learned Swedish -- which also uses that convention -- around the age of 10, I often found myself a little uncertain when hearing "half six" in English, as I grew up with the more explicit "half past six".

i'll let you work out whether those are "viertel nach fünf" (quarter past five) or "viertel vor sechs" (quarter to six), or "viertel nach sechs" (quarter past six), or "viertel vor sieben" (quarter two seven)