... since the Ethiopian church and the Eritrean church both make use of the Julian calendar, and not the calendar defined in Chapter 80.
That said, chapter 80 is historically interesting because...
So?
Enoch did not show God's geocentric calender ordinances in chapter 80.
The calendar Uriel showed Enoch begins in chapter 72, and ends in 82, with 80 being a discourse on the times of the sinners in the Tribulation.
In chapter 80 Uriel shows Enoch the days coming, when the orders of the sun, moon, and stars change course during the days of the sinners =the tribulation.
Isaiah and John, in Revelation both show the same.
Isaiah also states that the earth will be moved out of her place at that time, and jump about as a hunted Roe and will turn upside down and seasons will be backwards.
John also is told by the angel (messenger/angel is Enoch, there, who is dwelling with the Watcher angels in heaven and shows John the things to come, and also showed Daniel the things to come to Daniel's people in the last days -Daniel 10:21).
Enoch read all the tablets in heaven, and when showing John the things to come, John falls to his feet to worship him, twice, but the glorified human being showing John the things to come who came out of the temple of God in heaven (which temple is in the sun, as Scripture states, clearly), with a bowl of wrath to pour out on earth, told John not to do that, that he, himself, is a fellow prophet and a brother (a human being).
In those days of the tribulation, the messenger showing John everything states that the ordinances of heaven will be changed at that time, and the day and night portions of "one/echad "Day" will be shortened by 1/3 parts of them, each, making a whole day = 12 parts (roughly 16 hours as men are calculating them, in error, BTW).
Jesus also spoke of those days as being "HOT", and the days' parts "cut short" so that all flesh on earth will not perish (because of the sun's extreme heat in those days when earth is moved out of her place -signs in the heavens include that).