Barnabas is chapter 15, concerning the sabbath, which says...
1 Furthermore it was written concerning the Sabbath in the ten words which he spake on Mount Sinai face to face to Moses. "Sanctify also the Sabbath of the Lord with pure hands and a pure heart."
2 And in another place he says, "If my sons keep the Sabbath, then will I bestow my mercy upon them."
3 He speaks of the Sabbath at the beginning of the Creation, "And God made in 6x days the works of his hands and on the 7th day he made an end, and rested in it and sanctified it."
4 Notice, children, what is the meaning of "He made an end in 6 days"? He means this: that the Lord will make an end of everything in 6,000 years, for a day with him means a thousand years. And he himself is my witness when he says, "Lo, the day of the Lord shall be as a thousand years." So then, children, in 6 days, that is in 6 thousand years, everything will be completed.
5 "And he rested on the 7th day." This means, when his Son comes [at the start of that day of the week] he will destroy the time of the wicked one, and will judge the godless, and will change the sun and the moon and the stars, and then he will truly rest on the 7th day [Amen].
6 Furthermore he says, "Thou shalt sanctify it with clean hands and a pure heart." If, then, anyone has at present the power to keep holy the day which God made holy, by being pure in heart, we are altogether deceived.
7 See that we shall indeed keep it holy at that time, when we enjoy true rest, when we shall be able to do so because we have been made righteous ourselves and have received the promise, when there is no more sin, but all things have been made new by the Lord then we shall be able to keep it holy because we ourselves have first been made holy.
8 Furthermore he says to them, "Your new moons and the sabbaths I cannot endure." Do you see what he means? The present sabbaths are not acceptable to me, but that which I have made, in which I will give rest to all things and make the beginning of an eighth day, that is the beginning of another world. [the age to come]
9 Wherefore we also celebrate with gladness the eighth day in which Jesus also rose from the dead, and was made manifest, and ascended into Heaven (Chapter 15)
2 And in another place he says, "If my sons keep the Sabbath, then will I bestow my mercy upon them."
3 He speaks of the Sabbath at the beginning of the Creation, "And God made in 6x days the works of his hands and on the 7th day he made an end, and rested in it and sanctified it."
4 Notice, children, what is the meaning of "He made an end in 6 days"? He means this: that the Lord will make an end of everything in 6,000 years, for a day with him means a thousand years. And he himself is my witness when he says, "Lo, the day of the Lord shall be as a thousand years." So then, children, in 6 days, that is in 6 thousand years, everything will be completed.
5 "And he rested on the 7th day." This means, when his Son comes [at the start of that day of the week] he will destroy the time of the wicked one, and will judge the godless, and will change the sun and the moon and the stars, and then he will truly rest on the 7th day [Amen].
6 Furthermore he says, "Thou shalt sanctify it with clean hands and a pure heart." If, then, anyone has at present the power to keep holy the day which God made holy, by being pure in heart, we are altogether deceived.
7 See that we shall indeed keep it holy at that time, when we enjoy true rest, when we shall be able to do so because we have been made righteous ourselves and have received the promise, when there is no more sin, but all things have been made new by the Lord then we shall be able to keep it holy because we ourselves have first been made holy.
8 Furthermore he says to them, "Your new moons and the sabbaths I cannot endure." Do you see what he means? The present sabbaths are not acceptable to me, but that which I have made, in which I will give rest to all things and make the beginning of an eighth day, that is the beginning of another world. [the age to come]
9 Wherefore we also celebrate with gladness the eighth day in which Jesus also rose from the dead, and was made manifest, and ascended into Heaven (Chapter 15)
93.3 And Enoch then began to speak from a book, and said: "I was born the seventh, in the first week, [It doesn’t give reference as to when this week actually starts, however it appears that each week is a 700 year period for all ten of them to fit into a 7,000 year period. Interestingly this is like saying a week (7,000 years) ten times of weeks (700 years)! And since it says he was “born the seventh” (and there is a second witness to this in 1:14) I am making the start date of the first week on 3993 BC at the “founding of the world” when Adam sinned as it seems to fit perfectly throughout the whole “ten part” time period (one could use 3992 when Cain was born but in this scope of time it would make little difference]
91.15 And after this, matter on the tenth week [2309 - 3009AD], in the seventh part, [not “seventh day” - this seventh part being the last 100 years 2909AD-3009AD] there shall be an everlasting judgment [on the last day of the tenth week those who have died during the 1000 years will be brought out of the grave to be judged], which shall be executed by the Watchers of the eternal heaven [upon the archons or world rulers of this age]; the great judgment which shall come from all of the angels [the angels are the saints and the end of all that is evil will come as death itself is swallowed up forever - Amen!]
So here we have the basis of the 6,000 years of the Kingdom of Men from the founding of the world 3993 BC to the end of the world on 2309AD. The end of the Kingdom of Men in any event.