Time is referred to as follows: 

23:00~00:59 is called Zi Shi (子时).

01:00~02:59 is called Chou Shi (丑时).

03:00~04:59 is called Yin Shi (寅时)

05:00~06:59 is called Mao Shi (卯时)

07:00~08:59 is called Chen Shi (辰时)

09:00~10:59 is called Si Shi (巳时)

11:00~12:59 is called Wu Shi (午时)

13:00~14:59 is called Wei Shi (未时)

15:00~16:59 is called Shen Shi (申时)

17:00~18:59 is called You shi (酉时)

19:00~20:59 is called Xu Shi (戌时)

21:00~22:59 is called Hai Shi (亥时)

With the shi (时) means hour.

There is also another set which describes the time of the night which is:

19:00~20:59 is called Yi Geng(一更)

21:00~22:59 is called Er Geng(二更)

23:00~00:59 is called San Geng(三更)

01:00~02:59 is called Si Geng(四更)

03:00~04:59 is called Wu Geng(五更)

The second one can be translated as the First Night's Watch, Second, Third and so on.