John Gill Commentary Genesis 1:19

"And there was evening and there was morning, a fourth day." — Genesis 1:19 (ASV)

And the evening and the morning were the fourth day .
Made by the rotation of the earth on its own axis, in the space of twenty four hours: this according to Capellus was the twenty first of April, and according to Bishop Usher the twenty sixth of October; or, as others, the fourth of September: and thus, as on the fourth day of the creation the sun was made, or appeared, so in the fourth millennium the sun of righteousness arose on our earth.