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); (Genesis 1:14); (John 9:4); (John 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.