Genesis 1:14 (GNT)
Then God commanded, “Let lights appear in the sky to separate day from night and to show the time when days, years, and religious festivals begin
So, God knew that in the future people would tell the time and plan religious festivals according to what's going on with the celestial bodies
A day is one rotation of Planet Earth
And a year is one full orbit of the Sun, by Planet Earth
Months are also based on what the moon does too.
Days are divided into 24 pieces, each of which is divided into 60 pieces, and then 60 pieces again!
God didn't give us time, time has always existed
But he gave us the means to understand it and measure the rate at which it passes
He gave us a concept of time that is both linear (the days and years count up and progress in a straight line) and cyclical (once the Earth has rotated once it will rotate again, and again, and again...)
Our whole concept of time is derived from how often the Earth rotates and how long it takes it to perform one full orbit of the Sun - and what state the moon is in
I think it is amazing that ancient people were able to measure and observe all this
They didn't even have telescopes, it was all done by the naked eye
If someone told me to measure a year using only the celestial bodies I wouldn't know where to begin!
Ancient people weren't stupid - look at the pyramids of Egypt and all the philosophy they made
Also, it is worth noting that at the time of the creation account in Genesis God expected religious festivals to be performed by those he created!