Jesus called light into existence before He made the sun came to be: Day 1 (sun, light day).

The elements of the universe were made when there was already light without the sun shining from Jesus. John 1:4-9.

The elements of the universe were made when there was already shining light, the instantaneous light of or from Jesus which does not travel at the speed of the light of the sun.

Genesis 1:3-5 ASV
(3)  And God said, Let there be light: and there was light.
(4)  And God saw the light, that it was good: and God divided the light from the darkness.
(5)  And God called the light Day, and the darkness he called Night. And there was evening and there was morning, one day.

We read that the divisions of evening and morning began without the need of the rotation of the sun which was not created yet.

Note the sequence of the unit of a day (day) which is not a thousand years: darkness (night) and light (day), evening and morning.

The first day can be rightfully called 'light-day' or Sunday, mistaking the light of Jesus shining on our body of waters in the first day for the sun, since men perceived that it is the sun that lights up the world or want to discredit Jesus.

When Jesus lighted up the word of Himself, what was already there became visible. What did His light reveal that was already there hidden in the darkness?