Why is it important to ask?

The Bible says it is massively important

It keeps cropping up

Regarding the word day (yôm) several interpretations have been suggested. (1) The days of Creation refer to extended geological ages prior to man’s presence on earth. (2) The days are 24-hour periods in which God revealed His creative acts. (3) They are literal 24-hour days of divine activity. In favor of the third view is the fact that the term yôm with an ordinal (first, second, etc.) adjective means 24-hour days wherever this construction occurs in the Old Testament. Also the normal understanding of the fourth commandment () would suggest this interpretation.

Walvoord, John F. ; Zuck, Roy B. ; Dallas Theological Seminary: The Bible Knowledge Commentary : An Exposition of the Scriptures. Wheaton, IL : Victor Books, 1983-c1985, S. 1:28

 We need to think very carefully about this for we have a separation of light and darkness that appears to be nothing to do with a 24 -hour cycle.