I've never heard this before. What does "quarter of 10" mean? Is this
before 10 or after 10? I thought it was my hearing until this was
repeated. "quarter to" and "quarter after", rarely "quarter past" are all
usual ways of saying this around here. Though digital clocks make it "ten
fifteen". I think this must be a regionalism or slang for somewhere in the
USA (?).

I also hear "zulu" said instead of UTC (or the old GMT).