five o'clock

Short definition from Wiktionary

Noun

1. 1
   The start of the sixth hour of the day; 5:00 a.m. (05:00).
2. 2
   The start of the eighteenth hour of the day; 5:00 p.m. (17:00).
3. 3
   A position behind and slightly to the right (horizontal clock orientation) (from the location of the 5 mark on a clock face)