mid'-nit (chatsoth laylah, "middle of the night" (Ex 11:4; Job 34:20; Ps 119:62), chatsi ha-laylah, "the half of the night" (Ex 12:29; Jg 16:3; Ru 3:8), tokh ha-laylah, "the division of the night" and hence, the middle point (1Ki 3:20); meses nuktos (Mt 25:6), or meson tes nuktos, "the middle of the night" (Ac 27:27), mesonuktios, "midnight"; Westcott and Hort, The New Testament in Greek, mesonuktion (Ac 16:25, etc.)): In the period before the exile midnight does not seem to have been very accurately determined. The division of the night was into three watches, the middle one of which included midnight. In New Testament times the four-watch division was used where midnight must have been more or less accurately determined.
⇒See the definition of midnight in the KJV Dictionary