250th Millennium
From Tardis Wiki, the free Doctor Who reference
During the 250th Millennium, a series of Cyber Wars were fought between humanity and the Cybermen, organised into the Cyber Legions. (PROSE: The Secret Lives of Monsters)
A thousand years after the end of the Cyber Wars, three million Cybermen became active on Hedgewick's World of Wonders. Emperor Ludens Nimrod Kendrick Cord Longstaff XLI set off the Desolator to destroy the planet, killing every Cyberman there before they could escape, however a single Cybermite survived. (TV: Nightmare in Silver)