Sometimes the word “day” is used in the Bible to denote a long period of time. For example, the time of God’s judgment at the end of the age is called the Day of the Lord. And in Genesis 2:4 the entire creation period is called a day.
But could the days of creation have been such indeterminate periods of time?These are the generations of the heavens and the earth when they were created, in the day that the LORD God made the earth and the heavens.
The first day is described in Genesis 1:3-5.
The day included a period of light and a period of darkness. This day and each of those that followed it are described as consisting of an evening and a morning. It is clear that these were literal days, each one consisting of one rotation of the earth on its axis.And God said, “Let there be light,” and there was light. And God saw that the light was good. And God separated the light from the darkness. God called the light Day, and the darkness he called Night. And there was evening and there was morning, the first day.
Does this mean they were 24 hour days like the ones we have today? That would depend on whether the earth rotated at the same speed then that it does today.
The worldwide flood in Noah’s time involved more that just covering the world with water. The fact that the water in the oceans once covered the whole world shows that the surface of the earth was much flatter before the flood. After the flood the continents and islands rose up so that they were above the water.
Changes of this magnitude could have changed the speed of the earth’s rotation and thus changed the length of the day.The mountains rose, the valleys sank down to the place that you appointed for them. You set a boundary that they may not pass, so that they might not again cover the earth.
Psalm 104:8-9 ESV
The earliest calendars that we have any record of are based on a 360 day year with extra days added to bring the calendar into alignment with the seasons. Why didn’t they simple develop a 365 days calendar to begin with? One possible explanation is that before the flood there were only 360 days in a year and the first civilizations after the flood retained the old calendars instead of making new ones.
To calculate the possible length of a preflood day I first found the number of minutes in the extra 5 1/4 days. The result was 7,560 minutes. I then divided this by the 360 days and got 21 minutes. If our days were 21 minutes longer there would be 360 days in the year and the earliest calendars would have been accurate and not needed any adjustments. It seems possible that the days of creation were actually 24 hours and 21 minutes long.