The October Revolution was part of the Russian Revolution of 1917 which took place on 7 November 1917. Sasha claimed that his brother was killed in the fighting. (PROSE: History 101) As a result of the revolution, Tsar Nicholas II was executed and the monarchy was replaced with a communist government. (PROSE: The Clockwise Man)
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)