It was early in the fifth century, although nobody seemed too sure about exactly how early, when Dionysius Exiguus (Dennis the Short perhaps? Let’s call him Den. for short) was asked by his boss Pope John 1 to calculate the date of Easter for the next few years because the previous calculation only went as far as about 500 when the World was expected to end. (some of this may sound vaguely familiar)
Boadicea's Chariot 