1917

On 7 November 1917, the October Revolution took place in Russia. At the ceremony held in honour of the 50th anniversary of the Revolution in Red Square in Moscow on 7 November 1967, the Seventh Doctor explained to his companion Ace that the celebration of the October Revolution was held in November as Russia was still using the Julian calendar, which was eleven days behind the Gregorian calendar, in 1917. (AUDIO: Thin Ice) Sasha told the Eighth Doctor that his brother had been killed in the October Revolution. (PROSE: History 101)

Undated events
While hospitalised in Whitby, Reginald Tyler began writing The True History of Planets. He also met Enid Tyler during this time. (PROSE: Mad Dogs and Englishmen)

Emily Bostock and Harry Thompson disappeared into Swallow Woods. (PROSE: The Way Through the Woods)

A number of soldiers and other personnel involved in World War I — including Lt Jeremy Carstairs, Lady Jennifer Buckingham, Major Barrington and Captain Ransom — were transported to another planet by the War Lords, where they became unwitting players in an experiment. Later, the survivors were returned to Earth by the Time Lords. (TV: The War Games)

The Fifth Doctor, Peri Brown and Erimem visited Tibet and battled the Great Old Ones. (AUDIO: The Roof of the World)

The Seventh Doctor, Ace and Hex visited Charnage Hospital, a military hospital, in northern France. (AUDIO: No Man's Land)

The United States of America entered World War I. (AUDIO: The Sirens of Time) Among those who served were Solomon and Diagoras. (TV: Daleks in Manhattan)

George Newman fought on the Italian Front in the First World War. (AUDIO: Fiesta of the Damned)

After being touched by a Weeping Angel, the Twelfth Doctor wound up on Sto in 1917. Joining the cyborg rights movement, he spent the next century combatting the planet's prejudices. (COMIC: A Confusion of Angels)