Genesis 1:5

 Verse 5:

And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

comments:

I believe the first part of verse 5 is very simply stating that the divisions between light and dark were designated “Day” and “Night”, or, put another way, the time periods on Earth characterized by light and by darkness were termed daytime and nighttime.

It may be possible that the “first day” referred to at the end of verse 5 could be a literal reference to the first regular daytime period of time on the planet Earth as we know it, consisting of roughly 24 hours, or, more literally, that the verse referred to the end of that daytime and the beginning of the next daytime at the end of the nighttime when speaking of the evening and the following morning, or saying that the first official day began with the evening and morning following the day and night being named as such.  However, I also believe it is possible that it may not have literally been referring to that same designation of “day” as the first part of the verse referred to. After all, the reference to the creation of the sun and moon occurs later in the chapter; in the most literal sense the Earth may not have had an established 24-hour day before that time, but merely the concept or existence of light and dark. It may have simply been that whenever God was performing the work of creation, was present, or otherwise willed it, there was light upon the Earth and it was “daytime” - and whenever God willed there to be darkness, then it was “nighttime”. 

God existed before the Earth was formed, and I think it not unreasonable if the “days” of the creation might have been measured according to a length of time that also existed before the Earth was formed, such as “days” measured according to the days on some other sphere of existence, or by some other heavenly body that had been created previously, and which may have been vastly different lengths of time from the roughly 24-hour periods we associate with “days” on Earth.

Whether that may be the case or not, the formation of the Earth was still divided into steps or stages, a process of basically seven parts or phases, regardless of how much time each phase took, or even if each phase in that seven stage process took a different amount of time from the others, and the “days” listed were more like symbolic labels for the seven stages of the creation process.

Given the symbolic meaning that was afterwards given to the seven stages of Earth’s creation/formation (the last or seventh one being a period of rest), including and most notably in establishing a 7-day week with one day of rest for worship, I believe the most significant part of referring to the stages of creation as “days” was towards that end, regardless of whether the “days” mentioned were literal 24-hour Earth days, or literal “days” of a longer duration measured by some other heavenly body’s movements, or symbolic appellations for separate stages of creation which may not have all taken the same amount of time as each other (but each may have in any case still been periods of light and darkness, literally beginning or ending with an evening and a morning on Earth, for all I know)

Which is to say, that I believe the important part is not in how much actual time as currently measured on planet Earth each step of the creation process took, but in the division of the process into seven stages or parts, with planning and organization, and with the seventh part involving rest.