A revision was definitely necessary. The old version manufactures a precision which is neither in the Biblical text itself nor in the chronographers’ interpretations thereof. Anyone who has worked with Biblical chronology knows well how murky it can be--mainly because the Bible does not give us a solid chronology but merely implies one. Actually, the Bible actually implies several chronologies, as the Septuagint, Masoretic, and Samaritan recensions differ, often substantially.
Yet I don't think the revised Christmas Proclamation has quite solved the problem. In fact, it has imposed novelties of its own. Instead of exaggerated precision, it imposes an exaggerated ambiguity which seems completely divorced from Scripture: "unknown ages from the time when God created the heavens and the earth", and "several thousand years after the flood". Whatever we may think of the improved scientific accuracy behind the new Proclamation, we cannot lose sight of its liturgical purpose, which is to recap the whole of salvation history that has led us to the singular event of the Incarnation. Salvation history, of course, belongs more to the domain of Scripture than science, so it is rather odd in a liturgical context to suddenly throw the Scriptural text overboard and insert the language of cosmology.
There is, I think, a better way to revise the traditional Proclamation.
First, the Creation has to be dated not according to shaky chronologies cobbled together from the ages of the Patriarchs, but according to the same time scale that is operative in Genesis 1: the Six Days of Creation. A reader may take these days as either six 24-hour periods or unfathomably long ages--"days of the Lord"--but for the purposes of the Proclamation it is immaterial. The point is that they mean in the Martyrology the same thing they mean in Genesis, and that the Incarnation can be pinpointed to that seventh day--or age--when the Lord rested after he had created and adorned the Universe.
The second problem is the dating of the Deluge. Modern attempts to date the Flood range all over prehistory, which is why the new Proclamation is so vague on the point: "several thousand years". But these alternative theories, though intriguing and suitably cataclysmic, have no obvious connection to the Genesis account. It seems better to simply bring in the Deluge accounts of Mesopotamia, which almost everyone admits are closely related traditions that the Hebrews would have been familiar with and perhaps made use of in compiling Genesis. If the Scripture and the Mesopotamian texts indeed refer to the same event, then the Martyrology’s dating and the archaeology of Shuruppak (where the Sumerian flood legendarily occurred) are in agreement: 3000-2900 B.C. The flood at Shuruppak may not be the universal cataclysm we expect, but it is worth remembering that it was cataclysmic enough to be remembered and sung about for thousands of years. Until the matter is settled, I see no compelling reason to depart from the date as given.
From Abraham on, the problems of dating become much less pronounced. The chronographers may be off by a hundred years in any direction, but the approximate time periods are fairly well established, and the revisers of the Proclamation no doubt felt comfortable with them. Abraham, Moses, and David can be associated with dates around 2000, 1500, and 1000 B.C. respectively. The new Proclamation uses the term "centuries" rather than "years", which is not a bad solution, though the same ends could probably be achieved by simply reducing the significant figures in the traditional Proclamation: 2000 years, 1500 years, and 1000 years. Either solution is satisfactory, though the latter retains more of the traditional language.
After citing the prophetic weeks of Daniel, even the new Proclamation becomes very specific, with exact years being cited. But here, unlike previously, we have a good idea of the dates from non-Biblical sources. It seems best to simply leave the text as is. For instance, it is unclear when Rome was actually founded, but 753 BC was the traditional date as it was understood in antiquity.
Applying these principles, here is a proposed revision of the Christmas Proclamation of the Roman Martyrology:
In the seventh day of the creation of the world, when in the beginning God created heaven and earth; three thousand years from the flood; two thousand years from the birth of Abraham; one thousand five hundred years from Moses and the coming of the Israelites out of Egypt; one thousand years from the anointing of King David; in the sixty-fifth week, according to the prophecy of Daniel; in the one hundred and ninety-fourth Olympiad; in the year seven hundred and fifty-two from the founding of the city of Rome; in the forty-second year of the empire of Octavian Augustus, when the whole earth was at peace, in the sixth age of the world, Jesus Christ, eternal God, and Son of the eternal Father, desirous to sanctify the world by His most merciful coming, having been conceived of the Holy Ghost, and nine months having elapsed since His conception, is born in Bethlehem of Juda, having become man of the Virgin Mary.—THE NATIVITY OF OUR LORD JESUS CHRIST, ACCORDING TO THE FLESH.