Title text:
Geologists claim it’s because the earlier Cenozoic used to be called the Tertiary, but that’s just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won’t tell us about.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3120/
Related to the title text, some people are into that sort of thing:
Phantom time conspiracy theory is a pseudohistorical conspiracy theory first asserted by Heribert Illig in 1991. It hypothesizes a conspiracy by the Holy Roman Emperor Otto III and Pope Sylvester II to fabricate the Anno Domini dating system retroactively, in order to place them at the special year of AD 1000, and to rewrite history to legitimize Otto’s claim to the Holy Roman Empire. Illig believed that this was achieved through the alteration, misrepresentation and forgery of documentary and physical evidence. According to this scenario, the entire Carolingian period, including the figure of Charlemagne, is a fabrication, with a “phantom time” of 297 years (AD 614–911) added to the Early Middle Ages.
It has been feeling more and more like the 1700s around here lately.