20th century

On Earth, the 20th century was one of the most turbulent, violent, yet progressive centuries in the planet's history. In addition to major conflicts including the First (TV: To the Last Man) and Second World Wars (TV: The Empty Child / The Doctor Dances), humankind began to explore beyond their homeworld for the first time, and also began to make huge leaps in technological advancement. (TV: Day of the Moon) It was also during the 20th century that many world governments learned of the existence of extraterrestrial lifeforms (TV: Spearhead from Space), although the general public would remain in the dark about this until the beginning of the 21st century. (TV: Aliens of London) The Torchwood Institute, founded in the 19th century, began to gain power and influence in this century (TV: Fragments), while several attempted alien invasions resulted in the formation of the United Nations Intelligence Taskforce. (TV: The Web of Fear, The Invasion)

The Doctor had a great affinity for this century, though his first incarnation initially claimed to tolerate but not enjoy it. (TV: An Unearthly Child) He lived during this time period for several years as an exile from Gallifrey (during his third incarnation) (TV: Spearhead from Space, Doctor Who and the Silurians, et al.) and again for a number of months in 1913 and 1969 in his tenth incarnation (to name just two examples). (TV: Human Nature / The Family of Blood, Blink) Many of the Doctor's known Earth companions came from this century, as he visited it often. (TV: An Unearthly Child, The Massacre of St Bartholomew's Eve, The War Machines, Spearhead from Space, Terror of the Autons, The Time Warrior, et al.)