55th century

Tzim-Sha lived on the planet Ranskoor Av Kolos from 2018 to 5425. In this year, aided by the Ux, he planned to destroy Earth. He was stopped by the Thirteenth Doctor. Ryan Sinclair and Graham O'Brien imprisoned Tzim-Sha in a Stenza stasis chamber in suspended animation. The Ux sealed the building.

According to the Thirteenth Doctor, the years between 5418 and 5425 must have dragged on for Tzim-Sha. (TV: The Battle of Ranskoor Av Kolos)