(a) quarter of (a given hour in time)
A quarter of an hour (15 minutes) before the named hour in time (e.g., "quarter of six" would mean 5:45). Primarily heard in US. A: "What time does the movie start?" B: "Not until a quarter of eight, so we've got plenty of time!" I thought I'd be home already, but with this traffic, it'll be quarter of before I'm back.