Distant past
One Ice Age occurred in the time of early humans (TV: An Unearthly Child) and Neanderthals. (TV: Ghost Light) During this time, an Ice Warrior craft from Mars crashed and buried itself. (TV: The Ice Warriors) One Neanderthal was preserved by Light. (TV: Ghost Light) The Dæmons visited Earth, and according to the Third Doctor, inspired cave paintings of powerful supernatural beings. They favoured humans over Neanderthals, causing the latter to die out. (TV: The Dæmons)
In Birmingham during the Ice Age, the Eleventh Doctor and Amy Pond saved a group of Neanderthals who were being experimented upon by aliens. (COMIC: Snow Globe)
When Amy made a smart remark about the Doctor's suit, he warned her that the Ice Age was "a click away on the dial". (GAME: City of the Daleks)
When Majenta Pryce tried to activate the SKARDIS, it released a chronal wave which froze Sydney in ice from the Ice Age. (COMIC: The Age of Ice)
Earth suffered another Ice Age circa the year 5000, a time period visited by the Doctor during one of his four incarnations (TV: The Talons of Weng-Chiang) and, later in his life, during his fifth (AUDIO: The Butcher of Brisbane) and eighth incarnations. (PROSE: Emotional Chemistry) The Second Doctor met the thawed Ice Warriors during this time. (TV: The Ice Warriors)
Behind the scenes
Publicity material for The Ice Warriors set that story in the year 3000.