When I first read about the Phantom Time Hypothesis, I assumed it was the claim that time demonstrably drags while watching The Phantom Menace. Instead, it is one of the goofiest conspiracy theories I’ve ever come across.
Created by long-time crackpot Herbert Illig, the Phantom Time Hypothesis claims that everything we think occurred between AD 614 and AD 911 is, in fact, fraudulent and never happened. Important historical figures such as Charlemagne were made up out of whole cloth and never existed.
According to Illig, Holy Roman Emperor Otto III and Pope Sylvester II conspired to fake 300 years of history in the 7th century. Why? Because Otto wanted to rule during the Year 1000 to take advantage of Christian millenarianism. Uh huh.
Illig used to be active in Velikovsky-related organizations and you can see a bit of Velikovsky in this bit of reasoning, summarized by Wikipedia,
The relation between the Julian calendar, Gregorian calendar and the underlying astronomical solar or tropical year. The Julian calendar, introduced by Julius Caesar, was long known to introduce a discrepancy from the tropical year of around one day for each century that the calendar was in use. By the time the Gregorian calendar was introduced in AD 1582, Illig alleges that the old Julian calendar should have produced a discrepancy of thirteen days between it and the real (or tropical) calendar. Instead, the astronomers and mathematicians working for Pope Gregory XIII had found that the civil calendar needed to be adjusted by only ten days. (The Julian calendar day Thursday, 4 October 1582 was followed by the first day of the Gregorian calendar, Friday, 15 October 1582). From this, Illig concludes that the AD era had counted roughly three centuries which never existed.
With that sort of evidence, it is only a matter of time before The History Channel creates a television series dedicated to the idea.