The Old Tradition of Young-Earthism
Some Xian apologists have maintained that belief in Biblical inerrancy and literalism only began about 150 years ago or so; I pointed out counterevidence to one advocate of that sort of view, but he refused to accept it.
The counterevidence I pointed out was beliefs about the age of the Universe; I pointed out that Xian theologians had universally believed that the Universe is only 6000 or so years old before the progress of geology indicated that the Universe is much older than that. The dates would be calculated by adding up the Bible's begots and making a few assumptions here and there to fill in some of the blanks; the usual ages found are around 4000 BCE (Masoretic) and 5500 BCE (Septuagint). The Masoretic is a Hebrew version, while the Septuagint is a Hellenistic Greek translation. Wikipedia's article Dating Creation goes into a bit more detail about that.
One of the first to add up the begots was Rabbi Yossi ben Halafta (2nd century CE); he came up with 3760 BCE, at least according to Wikipedia's article on the Jewish calendar.
I do not know who first did that for the Septuagint, but the early Xian apologist Theophilus of Antioch (wrote around 180-185 CE) mentions a calculation in his Book III. He claimed that the Universe was created 5698 years before the death of Roman Emperor Marcus Aurelius, or 5519 BCE, which about fits for the Septuagint.
However, he noted that some pagans believed that the Universe is much older than that.
Apollonius the Egyptian claimed that the Universe is about 153,075 years old, though Theophilus later gives a figure of 15*10,375 = 155,625 years.
Plato claimed (Laws, Bk. 3) that the Earth has suffered numerous disasters that have destroyed most of humanity, like big floods survived only by hill people, and Theophilus claimed that he believed that most of humanity was destroyed by a great flood that happened 200 million years ago.
And some pagans believed that the Universe is eternal and uncreated.
And Augustine in his City of God (shortly after 410 CE) devotes a section (Bk. 18, Ch. 40) to " About the Most Mendacious Vanity of the Egyptians, in Which They Ascribe to Their Science an Antiquity of a Hundred Thousand Years." He harrumphed that the Universe is less than 6000 years old.
Other pagans also believed that the Universe was long-lived. Diogenes Laertius mentions some of them in the introductory part of his Lives and Opinions of Eminent Philosophers.
Some Egyptians claimed that Hephaestus/Ptah had revealed philosophy about 48,863 years before Alexander the Great's conquest of Egypt, or 49,194 BCE.
Hermodorus the Platonist claimed that Zoroaster had lived 15,000 years before the fall of Troy, or around 16,200 BCE.
Xanthus the Lydian claimed that Zoroaster had lived 6000 years before Xerxes crossed the Hellespont in the Persian Wars, or about 6500 BCE.
And elsewhere, the Hellenistic Babylonian priest and historian Berossus claimed that the ten kings who reigned before the Flood had done so for a total of 432,000 years (from Alexander Polyhistor's summary).