Guys, what I'm about to say might sound unbelievable but there is a lot of evidence to it and although it is not for certain it most certainly is reasonable. If you want to take a look into this interesting thesis you can check this presentation that is really well presented and it shows information that you can all go and look for if you want to -
https://www.youtube.com/watch?v=0DEAzA6TNR0It is interesting research and if you want to have a look at it
First of all they are known to have had amazing insight to the solar system which we only live to confirm after exploring it further and further.I am not that familiar with the exact details for the calendar but it was based on the movement of the planet in the soalr system, positions of the stars and the alignment of earth - moon - sun.
Their numeric system was based on 60 (we most commonly use numeric system based on 10 to do math) so it goes like 1 to 60 and then they calculate by times 60. Does this look familiar? 60 seconds in a minute. 60 minutes in an hour. 2x12x60 minutes in a day. 2x12x60. Close to 360 days in a year. There's a lot of reading about it and I'd like to read and learn more about them but those systems seem to have remained since ancient times. (I'm just speculating here but I'd like to look into the possible connection)
The more we read out of the millions of stone/clay tablets the more we find out that the biblical stories we read in the Holy Bible, have been a very limited and somewhat mistranslated version of the stories that we read in those tablets.
There were actual giants that lived at that time, which might be explained scientifically as well as with written texts with testimony and depictions of humanoid life forms far bigger then the rest in the same pictures and it's possible that they had different life span because they were different species and were refereed to as the Holy ones or the lofty ones.
Based on the stories left behind, those kings were called Anunaki (Anu - heaven or sky / na - to / ki - earth). They came from the sky flying and created the people using science (people who like these theory consider it genetic modification to enhance other species into becoming more like them).
There were also the ones called Igigi who are not mentioned too much because they were watchers and they were not interacting with people too much. (Common they is that they were watching from the heaven/sky/orbit).
In classic archaeology, things that did not fit the commonly accepted theory were either labeled as religious nonsense or were locked away so people cannot see them. If scientist take a look at those things, they find it fascinating and totally worth looking into. I'd like to keep an open mind and see what we may find out in the years to come.