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 remained 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 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.)

At some point in the 20th century, the Fisher King invaded the planet Tivoli and was there for ten years. The native Tivolians were liberated by the Arcateenians, but later enslaved by the very same race. (TV: Before the Flood)

It was also among the centuries endured by "Lady Me", formerly known as Ashildr, an 9th century Viking girl who was rendered effectively immortal when she was brought back to life by the Twelfth Doctor through a self-repairing Mire repair kit. (TV: The Woman Who Lived)