6
6:15 .
6:15
A quarter after five, half past 6, a quarter to 7, etc...
Quarter to 10.
It means it's 6:15
45 minutes till 7 o'clock is 6:15.
It is 06:15:00
6:05 to 6:45 40 minutes
4:45 ; Quarter to 5 5:15 ; Quarter past 5
Quarter past 12 !
A quarter past two!
Both are accepted, but "a quarter after" is preferred in formal writing.