How long is a day? Well, . . . which kind of day?

God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day. Genesis 1.5 NIV

Mathematician John Lennox points out that the word day is used in several different ways in Genesis 1 and 2.

Here, since it is contrasted with night, it means a 12-hour day, the period of daylight.

The second use of day, in this same verse, includes evening and morning and so of course would mean a 24-hour day.

Jump ahead to Genesis 2.2. After the six-time repetition of "and there was evening, and there was morning--the ___day," we come to the seventh day and see this phrase is missing. On this day, creation activity has stopped and God begins his reign over all that he has made. There's no end to this day of God's ceasing to create and beginning to rest (or rule clarifies John Walton). It is on-going until now. Lennox says, ". . . we are still today in God's Sabbath rest." So the seventh day in this case is what St. Augustine looked at as "an epoch that extends onward into eternity."

Finally, consider Genesis 2.4. Although the NIV uses when, other translations more accurately translate that Hebrew as "in the day that." NASB, AMP, ESV, and Young's Literal all say, "in the day that" the Lord God made the earth and the heavens . . . . In this case, it's like saying, "In my day, we did it this way." It means an era of time.

Thanks to John Lennox (7 Days That Divide the World) for these examples.

Again something to think about as we consider how to read the Bible.