Epistle of Barnabas on Sabbath

I was doing some research on how the early Apostolic Fathers viewed the Sabbath and the day they gathered. Here is the Lightfoot translation the Epistle of Barnabas, written 80-120 CE. Note this Sabbath view and theory. Interesting that I heard some fringe Adventist espouse this same 6000 year and then the end of the world theory. But note that even at this early date they "kept" the eighth day in reverence or as a memorial of the resurrection. No it doesn't mean the Sabbath was "changed" - this is just a reporting on what they did.

Barnabas 15:3
Of the Sabbath He speaketh in the beginning of the creation; And God made the works of His hands in six days, and He ended on the seventh day, and rested on it, and He hallowed it.

Barnabas 15:4
Give heed, children, what this meaneth; He ended in six days. He meaneth this, that in six thousand years the Lord shall bring all things to an end; for the day with Him signifyeth a thousand years; and this He himself beareth me witness, saying; Behold, the day of the Lord shall be as a thousand years. Therefore, children, in six days, that is in six thousand years, everything shall come to an end.

Barnabas 15:5
And He rested on the seventh day. this He meaneth; when His Son shall come, and shall abolish the time of the Lawless One, and shall judge the ungodly, and shall change the sun and the moon and the stars, then shall he truly rest on the seventh day.

Barnabas 15:6
Yea and furthermore He saith; Thou shalt hallow it with pure hands and with a pure heart. If therefore a man is able now to hallow the day which God hallowed, though he be pure in heart, we have gone utterly astray.

Barnabas 15:7
But if after all then and not till then shall we truly rest and hallow it, when we shall ourselves be able to do so after being justified and receiving the promise, when iniquity is no more and all things have been made new by the Lord, we shall be able to hallow it then, because we ourselves shall have been hallowed first.

Barnabas 15:8
Finally He saith to them; Your new moons and your Sabbaths I cannot away with. Ye see what is His meaning ; it is not your present Sabbaths that are acceptable [unto Me], but the Sabbath which I have made, in the which, when I have set all things at rest, I will make the beginning of the eighth day which is the beginning of another world.

Barnabas 15:9
Wherefore also we keep the eighth day for rejoicing, in the which also Jesus rose from the dead, and having been manifested ascended into the heavens.

See also Chapter 4 of the Epistle of Mathetes to Diognetus