They are 7- 24 hour periods, just as God tells you in His Book. The evening and the morning were the first day, and so on. He wanted us to KNOW just how long it was for a purpose. That is why Jews start their day in the evening and end it in the morning. Isn't it weird that humans try to do EVERYTHING different from God?
The reason for the 7 days is explained when He tells us " A day is as a thousand years." What he means is there will be 6000 years of separation from Him and the day of rest will come with the 1000 year reign of Christ on Earth. Ergo, 7000 years of history on Earth. Then will come a new heaven and a new Earth. Not much is said about later than that, but if you didn't make the cut on Earth, it won't matter after that.
Jewish scholars figure that from Adam to the Flood was about 1800-1900 years. From the flood to Jesus was about 2000 years or so. There is disputes during the times of captivity, I believe. Then from Jesus to today is about 2003-2010 years. We don't know the exact year because of calendar changes and leap years in the Julian calendar. I think the Jews have a second repeated month every few years or so to fix the leap years. WE SHOULD BE VERY CLOSE TO THE RETURN OF JESUS!
The first and second Passovers have already happened. The first and second Unleavened Bread and First Fruits has already happened. The first and second Pentecost has already happened.The only Feasts days left to be repeated are, Rosh Hashanah, Yom Kippur, and Tabernacles.
Rosh Hashanah should be the Rapture of the Church. The people that were riding over the countryside during this Feast day heard the Shofar( or trumpet) blown for 2 days from every town they passed, ergo, the "day no one knows". Yom Kippur is the highest Holy day, Judgment Day( the end of things as we know it), and Tabernacles, the day Jesus (and the Church) comes back to rule and reign for 1000 years on Earth. Ergo 7 days to God is 7000 years for mankind.
Prior to the creation of the Sun and the Moon, what did the terms "evening" and "morning" mean?