Bicycle invented in 12th century or 1817? What is the true?

In May 2008, archaeologists from the University of Bristol, while excavating the grounds of Château Gaillard in France, made a sensational discovery dating back to the 12th century. At a depth of 2 meters, a bicycle was found. It is very similar to modern bicycles, but has armor, sword-hilt handles, and horsehair instead of tires on the wheels.

So how come?... History and science say that the bicycle was invented in 1817...