4221

43K2.1 was a date in the 42nd century. Sanctuary Base 6 was assaulted by the Beast, which was defeated by the Tenth Doctor and Rose Tyler. (DW: The Impossible Planet / The Satan Pit)

''How this date related to the Gregorian calendar is unknown. Its setting in the 42nd century was confirmed by the Tenth Doctor when he spoke of this encounter again to Donna. (DW: Planet of the Ood)''