1915

Sometime in April or May, the Doctor was wounded at Gallipoli. (TV: The Sea Devils)

On 7 May, the RMS Lusitania was torpedoed by the U-20, an act that helped provoke the United States of America into entering World War I two years later. One of the people killed onboard was a petty criminal named Eric Charles Vincent. (AUDIO: The Sirens of Time)

In August, the Seventh Doctor, Ace and Bernice Summerfield arrived in Haiti. (PROSE: White Darkness)

The Doctor met Harry Houdini. (TV: Planet of the Spiders, TV: Revenge of the Cybermen)

Alternative timelines
In John Smith's possible future, he married Joan Redfern this year. (PROSE: Human Nature)

In another alternative timeline, the Lusitania did not sink on 7 May due to the Fifth Doctor's intervention. Eric Charles Vincent, having survived, went on to kill Alexander Fleming in a botched robbery attempt in December 1927 before the biologist discovered penicillin. Without the protection offered by penicillin, Earth fell prey to new strains of meningitis and pneumonia in 1956. The survivors never developed a space programme. Consequently, the Knights of Velyshaa were not defeated by the Earth Alliance in 3562 as they otherwise would have been. (AUDIO: The Sirens of Time)