Yearometer

The yearometer, or year meter, (COMIC: The Doctor Strikes Back) was an instrument in the Doctor's TARDIS that showed the TARDIS' position in time and space. It stopped calculating properly after the First Doctor left England in November 1963. (TV: "The Cave of Skulls") According to another account, the yearometer had been damaged on a previous expedition. (PROSE: Doctor Who in an Exciting Adventure with the Daleks)

When the TARDIS arrived at Byzantium, the yearometer gave the date as 14 March 64. (PROSE: Byzantium!)

When the TARDIS arrived at Marpling, the yearometer gave the date as 27 August 1933, though Anji Kapoor was incredulous that it was named this. (PROSE: Eater of Wasps)

When Bill Potts questioned if they really were in an alternate 2017, and not the 22nd century, the Twelfth Doctor assured her that the TARDIS had a yearometer. (AUDIO: Emancipation of the Daleks)