Six Ages of the World

[3] The Six Ages, as formulated by Augustine of Hippo, are defined in De catechizandis rudibus (On the catechizing of the uninstructed), Chapter 22: The Ages reflect the seven days of creation, of which the last day is the rest of Sabbath, illustrating the human journey to find eternal rest with God, a common Christian belief.

[5]The Zohar explains: The redemption of Israel will come about through the mystic force of the letter "Vav" [which has the numerical value of six], namely, in the sixth millennium. ...

Happy are those who will be left alive at the end of the sixth millennium to enter the Shabbat, which is the seventh millennium; for that is a day set apart for the Holy One on which to effect the union of new souls with old souls in the world (Zohar, Vayera 119a).Elaborating on this theme are numerous early and late Jewish scholars, including the Ramban,[6] Isaac Abrabanel,[7] Abraham Ibn Ezra,[8] Rabbeinu Bachya,[9] the Vilna Gaon,[10] the Lubavitcher Rebbe,[11] the Ramchal,[12] Aryeh Kaplan,[13] and Rebbetzin Esther Jungreis.

The interpretation was taken to mean that mankind would live through six 1,000 year periods (or "days"), with the seventh being eternity in heaven or according to the Nicene Creed, a World to Come.

Hippolytus said that the measurements of the Ark of the Covenant added up to five and one-half cubits, meaning five and a half thousand years.