Zec 14:8 And it shall be in that day, that living waters shall go out from Jerusalem; half of them toward the former sea, and half of them toward the hinder sea: in summer and in winter shall it be.
Here we see a 'day' being summer & winter which isn't a 24hr period. The symbolism of morning and night are between order, light, birth, progress and the night is the end of that process. It does not signify a 24 hr period of time.
It is simply describing that at the beginning of that age or purpose. God had already created the heavens and the earth but he created (asah) as they are now.
Each yowm was a process with a beginning (day) and an end (evening or night) That is the symbology.
The pattern is of symbolism, not literalism.
Gleason Archer, Professor of Old Testament and Semitics at Trinity Evangelical Divinity School, who concludes that "Entirely apart from any findings of modern science or challenges of contemporary scientism, the twenty-four-hour theory was never correct and should never have been believed."