I’m sure many of you will have seen this claim in online discussions with Creationists. Estimates on the age of the universe based on biblical sources were prevant during the heyday of the Atheist-Creationist conflict. Of course, this is no new thing, but old as Christianity itself.
From early on some Church Father realized that the Bible contained dates and clues that oculd be used to estimate the age of the world. It was the Byzantine Empire that enshrined one of these estimates by law and used the Creation in September 1st of 5509 B.C. as a basis for its calendar. It sounds funny, but this Anno Mundi Calendar was used for many centuries. It first appeared in the 7th century and started getting replaced in the Orthodox World by “A.D.” and “B.C.” just in the 16th century (in Russia it was changed by Peter the Great in the 1700s).
This is also the source of the well-known image from the website of the Patriarchate of Jerusalem, which has been amply mocked by the greek atheist community.