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St Augustine in Civitas Dei gives the different chronologies of the various civilizations, and if I recall, even the Egyptians estimate the earth to be about 10,000 years old, according to Augustine.  But the Doctor of Grace does say that it matters not if we believe that the earth is eons old.  What we cannot say is that The Fall did not happen, or that God did not immediately create Adam and Eve, etc. 

The problem is, that the majority of those who hold that the earth is millions of years old tend to be evolutionists.  A Catholic is allowed to be a heliocentrist, but he cannot deny what was aforementioned. If a Catholic were obligated to believe a particular number of years - let us say, six thousand, seven thousand, no, ten thousand, et alia, there would be mayhem.  Sometimes numbers can be tricky.  Blessed Anne Emmerich says that there were over a hundred people on the Ark, and this is not against Faith.  When St. Peter says, "eight souls were saved through water,"  we can safely maintain that there were ninety more souls.  But we cannot say, "Only six souls were saved through water," as this would obviously imply heresy.  Now, if St. Peter had said "only eight souls were saved by water," then we would be obligated to believe only eight souls. But Scripture does not include the qualifier "only." 

It seems she did St Giles. I only learned that recently. But it makes sense.

https://ronconte.com/2014/02/27/noah-and-the-flood-according-to-the-visions-of-blessed-anne-catherine-emmerich/

'The ark, lying there by itself on the top of the hill, shone with a bluish light. At a distance, it looked as if it were descending from the clouds. And now the time for the Deluge drew nigh. Noah had already announced it to his family. He took with him into the ark Shem, Ham, and Japheth with their wives and their children. There were in the ark grandsons from fifty to eighty years old with their children small and large. All that had labored at its construction and who were good and free from idolatry, entered with Noah.

There were over one hundred people in the ark, and they were necessary to give daily food to the animals and to clean after them. I must say, for I always see it so, that Shem’s, Ham’s and Japheth’s children all went into the ark. There were many little boys and girls in it, in fact all of Noah’s family that were good. Holy Scripture mentions only three of Adam’s children, Cain, Abel, and Seth; and yet I see many others among them, and I always see them in pairs, boys and girls.'