0
According to the Eighth Doctor, "round about 0 BC, AD", the first Christmas took place. He went to attend it with Leonardo da Vinci. (AUDIO: Relative Dimensions) Indeed, both he, news stations in San Francisco, at least a significant portion of the staff of Walker General Hospital, and noted scholars like Professor Wagg believed that the year 2000 started a new millennium, thus indicating that there was a year zero. (TV: Doctor Who)
Others felt that year zero was a fiction. Both the Sixth Doctor and Anji Kapoor's ex-boyfriend Dave Young passionately argued against the existence of a year zero. (PROSE: Millennium Shock, Escape Velocity)
Behind the scenes
In the real world, in the common Western calendar, the year "zero" does not exist, with a direct progression from 1 BC to 1 AD. Nevertheless, because a case for the existence of year 0 can easily be built from significant DWU sources, and because it is easier to build some mathematical templates on this wiki, the Tardis community chooses to believe the Eighth Doctor's view on the matter over the Sixth's]].