“18. And Jared lived a hundred and sixty two years, and he begot Enoch. 19. And Jared lived after he had begotten Enoch eight hundred years, and he begot sons and daughters. 20. And all the days of Jared were nine hundred and sixty two years, and he died. 21. And Enoch lived sixty five years, and he begot Methuselah. 22. And Enoch walked with God after he had begotten Methuselah, three hundred years, and he begot sons and daughters. 23. And all the days of Enoch were three hundred and sixty five years. 24. And Enoch walked with God, and he was no longer, for God had taken him.”—Torah,Bereishit 5:18-24
Sir Walter Raleigh, in his History of the World (written in 1616 while imprisoned in the Tower of London), makes the curious assertion that part of the Book of Enoch "which contained the course of the stars, their names and motions" had been discovered in Saba in the 1st century and was thus available to Origen and Tertullian. He attributes this information to Origen's Hom. in Num.1, though no such statement is found anywhere in extant versions of Origen.
Four fragmentary editions of the Astronomical Book were found at Qumran, 4Q208-211. 4Q208 and 4Q209 have been dated to the beginning of the 2nd century BC, providing a terminus ante quem for the Astronomical Book of the 3rd century BC, if not earlier. The fragments found in Qumran also include material not contained in the later versions of the Book of Enoch.
This book contains descriptions of the movement of heavenly bodies and of the firmament, as a knowledge revealed to Enoch in his trips to Heaven guided by Uriel, and it describes a Solar calendar that was later described also in the Book of Jubilees which was used by the Dead Sea sect. The use of this calendar made it impossible to celebrate the festivals simultaneously with the Temple of Jerusalem.
The year was composed from 364 days, divided in 4 equal seasons of 91 days each. Each season was composed of three equal months of 30 days, plus an extra day at the end of the third month. The whole year was thus composed of exactly 52 weeks, and every calendar day occurred always on the same day of the week. Each year and each season started always on Wednesday, which was the fourth day of the creation narrated in Genesis, the day when the lights in the sky, the seasons, the days and the years were created. It is not known how they used to reconcile this calendar with the tropical year of 365.24 days (at least seven suggestions have been made), and it is not even sure if they felt the need to adjust it.