And God called the light Day, and the darkness he called Night.

Scofield Reference

Genesis 1:5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

The word "day" is used in Scripture in three ways: (1) that part of the solar day of twenty-four hours which is light Genesis 1:5,14; John 9:4; 11:9. (2) such a day, set apart for some distinctive purpose, as, "day of atonement" (Leviticus 23:27); "day of judgment" Matthew 10:15. (3) a period of time, long or short, during which certain revealed purposes of God are to be accomplished, as "day of the Lord." evening The use of "evening" and "morning" may be held to limit "day" to the solar day; but the frequent parabolic use of natural phenomena may warrant the conclusion that each creative "day" was a period of time marked off by a beginning and ending.

Verse Reference

Genesis 1:14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years.

John 9:4 I must work the works of him that sent me, while it is day: the night cometh, when no man can work.

John 11:9 Jesus answered, Are there not twelve hours in the day? If any man walk in the day, he stumbleth not, because he seeth the light of this world.

Leviticus 23:27 Also on the tenth [day] of this seventh month [there shall be] a day of atonement: it shall be an holy convocation unto you; and ye shall afflict your souls, and offer an offering made by fire unto the Lord.

Matthew 10:15 Verily I say unto you, It shall be more tolerable for the land of Sodom and Gomorrha in the day of judgment, than for that city.