In olden china, the night was split into five periods. 五更 refers to 3-5am in current time period and 五更 was used to signify the changing from night to day.
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There’s a chinese proverb that goes 俗话说：“一更人，二更锣，三更鬼，四更贼，五更鸡。”
This translates to: “first period human, second period gong, third period ghost, fourth period thief and fifth period chicken.
What this means is that during the first period, there is still human activity, therefore it is named human. It spans from 7-9pm.
During the second period, two sounds of gong and two sound of clappers signify a point of time during the second period. Therefore it is named gong. During this time, people would already be preparing to sleep already. It spans from 9pm-11pm.
During the third period, it is said to be the darkest and quietest point at night. Legend has it that ghosts come out during this period. Therefore, the third period is named ghost. It spans from 11pm-1am.
During the fourth period, the sky is slowly beginning to turn brighter. Although it is still dark, it is brighter than the third period. Also, this is the point in time where people are in their deepest sleep. It is said that at this time, thieves start to steal. Therefore, the fourth period is called thief. It spans from 1am-3am
The fifth and last period of the night is named the chicken and it signifies the changing from night to day. At this time, the roosters crow in the morning to wake the people up. This period spans from 3am-5am.