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

The division of the day by hours is first mentioned in Daniel 3:6 Daniel 3:15 ; 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 ( Genesis 2:4 ; Isaiah 22:5 ; Hebrews 3:8 , etc.). In Job 3:1 it denotes a birthday, and in Isaiah 2:12 , Acts 17:31 , and 2 Timothy 1:18 , the great day of final judgment.

These dictionary topics are from
M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition,
published by Thomas Nelson, 1897. Public Domain, copy freely.