Day

The Jews reckoned the day from sunset to sunset (Lev. 23:32). It
was originally divided into three parts (Ps. 55:17). "The heat
of the day" (1 Sam. 11:11; Neh. 7:3) was at our nine o'clock,
and "the cool of the day" just before sunset (Gen. 3:8). Before
the Captivity the Jews divided the night into three watches, (1)
from sunset to midnight (Lam. 2:19); (2) from midnight till the
cock-crowing (Judg. 7:19); and (3) from the cock-crowing till
sunrise (Ex. 14:24). In the New Testament the division of the
Greeks and Romans into four watches was adopted (Mark 13:35).
(See WATCHES T0003789.)

The division of the day by hours is first mentioned in Dan.
3:6, 15; 4:19; 5:5. This mode of reckoning was borrowed from the
Chaldeans. The reckoning of twelve hours was from sunrise to
sunset, and accordingly the hours were of variable length (John
11:9).

The word "day" sometimes signifies an indefinite time (Gen.
2:4; Isa. 22:5; Heb. 3:8, etc.). In Job 3:1 it denotes a
birthday, and in Isa. 2:12, Acts 17:31, and 2 Tim. 1:18, the
great day of final judgment.