The rearrangement of the Christmas proclamation in the new martyrology, which removed the crisp specificity of the Hebrew dates from Genesis and the Flood to the time of Our Lord (5,199 and 2,957 years respectively) in favor of the more tediously cosmic "unknown ages," is probably one of those revisions that while frustrating to the poetic and mythically-minded, is is to be tolerated on the grounds of prudence, lest we give religion reporters, who are scriptural literalists in ways the Fathers of the Church could ever imagine, yet more ammunition to chuck at us.

Perhaps in a more civilized time, that understands the symbolic value of the Hebrew chronology and its peculiar prominence in this momentous declaration, we can reinstate it without fear of turning it into a zero-sum binary debate between science and religion. (Of course, with the Motu Proprio, both proclamations now are still out there in some sense, side by side.) What seems to me less justifiable was the excision of the final, almost Tolkeinesque designation, "in the sixth age of mankind." What does this signify?

The concept of mankind's Six Ages was first articulated by St. Augustine in De catechizandis rudibus, though there are Jewish roots to the concept, which also reflects the six days of creation in Genesis (which, if there are any religion reporters listening, also need not be taken literally, though let's get this straight, God was the one doing the creating.) The six ages takes us through the whole of human history, with the seventh age, like the seventh day, being our life in heaven. Viz., from St. Augustine:

The First Age: "The first is from the beginning of the human race, that is, from Adam, who was the first man that was made, down to Noah, who constructed the ark at the time of the flood."
The Second Age: "..extends from that period on to Abraham, who was called the father indeed of all nations.."
The Third Age: "For the third age extends from Abraham on to David the king."
The Fourth Age: "The fourth from David on to that captivity whereby the people of God passed over into Babylonia."
The Fifth Age: "The fifth from that transmigration down to the advent of our Lord Jesus Christ."
The Sixth Age: "With His [Jesus Christ's] coming the sixth age has entered on its process."

Note also that the sixth age is more-or-less identical to the concept of the Milennium in the Apocalypse which is not, as some sorts of Protestants might have it, Christ's reign on earth in the end-times, but His reign through His Church on earth. In addition to the days of the week, this schema also may fit, with some tweaks, into the Liturgical Year as well, though there it was divided into four periods by Bl. Jacobus de Voragine in the Legenda Aurea, who speaks of:

1. The Time of Deviation: from Adam's turning away from God, thence to Moses, which is represented from the period from Septuagesima to Easter [i.e., beginning some weeks before Lent].
2. The Time of Renewal: From Moses to the birth of Christ, represented by Advent.
3. The Time of Reconciliation: When we ourselves are reconciled to Christ, which is represented by Easter to Pentecost.
4. The Time of Pilgrimage: Which is our own pilgrimage with Christ in the present day, represented by the period from Pentecost to Advent, where, Jacobus reports, the bellicose books of Kings and Maccabees are read (presumably in the office), to represent our own various spiritual struggles.

This fourfold arrangement also relates to the seasons of the year, with winter being analogous to the first, spring the second, summer the third, fall the fourth; Jacobus also compares it to four periods of the day as well. And while some of this may seem a bit out of sequence, Jacobus explains, to start with the period of deviation (Lent), rather than the period of renewal (Advent), would be to put error, rather than aspiration, first: "[F]or she [the Church] puts reality before the sequence of time, just as the Evangelists often do."