6000 will be the last year, the year when Messiah will arrive and usher in the redemption, is a belief that makes a lot of people try to calculate when that is. This world, as we know it, will last for six thousand years, with the seventh millennium ushering in the cosmic Shabbat, the Messianic Era. Six days a week we work, and on the Shabbat we rest and enjoy the fruits of our labor; the same is true with millenniums.
Everyone is, of course, aware of the institution of the "Sabbath for man" in Genesis, which is also in the Ten Commandments. A week of days consists of six days for labor, followed by a day of rest.
It is interesting that this pattern is again replicated in several other ways.
1. "Week of Weeks," or "Counting of the Omer," between the Feast of First Fruits and the Feast of Weeks, in Hebrew, Hag HaShavuot. This was also the time between our First Fruits (the Resurrection) and the born again experience of the believers in assembly at Pentecost.
2. "Week of Months," is from Passover in the Exodus, between the month of Nisan, to Tishri, at Rosh Hashannah.
3. "Week of Years" can be found in the Sabbatical year, where is a Sabbath rest for the land. After six years of cultivation, they were to allow the land to rest for a year.
4. "Week of Millenniums" If there are "weeks" (groups of seven) of days, weeks, months, and years, what about millennia? Nachmonides (1194-1270) wrote about the Sabbatical Millennium, 6,000 years of man's attempts to govern himself, followed by 1,000 years of God's perfect rule, for a total of 7,000. Revelation talks about the Millennial Rest.