Do you remember the years 614-911 AD? Of course you don't.
Because allegedly, they never happened. And everything you think you've seen from that era is an elaborate fake meant to disguise the fact that we actually live in the year 1713.
Yes. Someone actually thinks this. Specifically, a Heribert Illig of Germany. The theory goes that when the switch was made from the Juilian calendar to the Gregorian, there should have been, according to Illig's math. a discrepancy of thirteen days to correct, as the calendar deviated from the solar year by 10.8 minutes per year, or about one day per century. As it turned out, it was only adjusted by ten days.
Illig took this to mean there were three centuries somewhere that never happened and immediately went off looking for conspiracy theories. You can see here how such a theory eventually expanded to include the whole wide world.
Raids of the Vikings were used to justify the lack of edifices within the west. They came in spring-time, every year, and burnt and looted the countries, before they retired before the winter. [Kinder/Hilgemann 131] Archaeologically, these pillages left no traces. [WU 97 ff.] Subsequent military expeditions of the Saracens were named to explain the missing of medieval churches in Georgia and Armenia.
You had better believe people have gotten their shots in.
Never mind the possibility that Illig just had his math wrong and that the ten-day adjustment was correct after all. Which he did, and it was.