It's 5:00. / It's five.
It's 5 o'clock.
It's 5 A.M. / It's 5 P.M.
It's exactly 5 o'clock.
It's exactly 5 A.M. (P.M.)
It's 5 (o'clock / A.M. /P.M.) on the dot.
It's 5 (o'clock / A.M. /P.M.) sharp.
It's five in the morning /in the afternoon.
