History seems to start with the birth of Christ. Before Christ is far, as it were it is unclear and so it is unimportant.
We Muslims used to have the Hegira Calendar. Before the Hegira, after the Hegira... On December 26th 1925, we adopted the Gregorian Calendar, and we considered the beginning of our calendar as Year Zero.
However, the Sumerians were using far more advanced calendars than those we used to have. In fact, 3000 years before Plato, they knew the Great Year.
The Great Year ( Precession or Precession of the Earth )
Due to the precession of the North-South axis of the Earth, the Pole Star actually draws a large circle in the north. It is needed to take 25,920 years for the Polar Star to arrive at the same spot. This process is named as the Great Year. Western Civilization, who admire Greek Civilization, has given the name of ''The Great Year'' long after. Platon had found out this period of time from Minoan Civilization. Minoans had found out it from Egyptians, and Egyptians had found out it from Sumerians.
A document registered in the Vat.7847 catalog number at the Berlin Museum gives us the information about The Great Year about 6,000 years ago.
http://therealsamizdat.com/tag/lunar-phases/
This information, in fact, should not make our eyes pop, but it should help us to think over. How did the Sumerians, the oldest known society, suddenly appeared in 4000s, know this knowledge? Let's go through what they know, how this information would stand them in good stead? There are various speculations on this subject. The world's respected scientists can explain it. However, I would like to clarify the issue by approaching in a completely different perspective as a contribution to these explanations.
If we can visualize in our minds where we are in time, we will see that even the most imaginative theories of the scientists should be taken into account.
It is not possible to know how much time has passed since God created time for sure. However, there are clues in the Qur'an that the time is relative. Theologians already explain what these clues are. Modern science is now in agreement with the universe is 13.8 billion years old and the Earth is 4.5 billion years old. This seems to be quite true both mathematically and support of physical evidence.
A copy of the Vat.7847 tablet in Berlin Museum: