This is in reference to Genesis from the Bible, where it speaks of creating the world in 6 days.

I think one of the strongest reasons to suggest that when a day is spoken in the creation use of day, is that it actually describes the days as day and night, a 24 hour period.

Genesis 1:3-5
3 And God said, "Let there be light," and there was light. 4 God saw that the light was good, and He separated the light from the darkness. 5 God called the light "day," and the darkness he called "night." And there was evening, and there was morning—the first day.

It describes the first day as morning evening, day and night. That's just not suggestive at all to be a longer period of time.

But further, it goes on. After each day of creation, it speaks of this time period of morning and evening passing, and another day.

Genesis 1:8
8 God called the expanse "sky." And there was evening, and there was morning—the second day.


Genesis 1:13
13 And there was evening, and there was morning—the third day.

Genesis 1:19
19 And there was evening, and there was morning—the fourth day.

Genesis 1:23
23 And there was evening, and there was morning—the fifth day.

Genesis 1:31
31 God saw all that he had made, and it was very good. And there was evening, and there was morning—the sixth day.

How many mornings and evenings are in an age? Could be hundreds, thousands, more? But in a 24 hour period, there is only one of each.

In Exodus 20:11 we see,
11 For in six days the LORD made the heavens and the earth, the sea, and all that is in them, but he rested on the seventh day. Therefore the LORD blessed the Sabbath day and made it holy.