Leupold Genesis part 33 verse 5

5. And God called the light day and the darkness He called night. Then came evening, then came morning-the first day.

On "came evening" see v. 8; also on the derivation of "evening."

To appreciate what this act means it is necessary to bear in mind what the Hebrew idea of giving a name or "calling a name" to an object implies. For this includes not only finding a convenient label to attach to a thing that it might thereby be identified, but especially the idea of expressing the very nature of a thing. In this act God did not find names for man to use when speaking of day and night; there was not even a man present to hear these names. But this act reports that God fixed day and night separately for their respective purposes. This concluded the first day's work, for now the light prevailed that man might put it to the uses for which God intended it, and night was fixed to fit the general scheme.

In the interest of accuracy it should be noted that within the confines of this one verse the word "day" is used in two different senses. "Day" (yom) over against "night" (lssyelah) must refer to the light part of the day, roughly, a twelve hour period. When the verse concludes with the statement that the first "day" (yom) is concluded, the term must mean a twenty-four hour period. If any attempt is made to fix the time of the year when the creative work was done, the vernal equinox seems most likely to fit the needs of the case.