25th century

In the 25th century, the planet Earth, under a repressive government, had a population of a hundred billion people, most of them living on floating islands. It was a highly polluted planet. (TV: Colony in Space) Most Earth colonies during this time were "terrible places." (PROSE: Christmas on a Rational Planet)

Schooling was quick. Students obtained certificates in a vast range of disciplines by the age of ten. They were taught by machines for one hour a week. In comparison, a 20th century high school was like a nursery. (TV: The Web Planet)

Both Vicki Pallister and Nikki Jupiter, companions of the First and Tenth Doctors respectively, were natives of this century.

Prior to this century, World War IV was fought on Earth. On a visit to London in February 1814, Vicki noted that St Paul's Cathedral survived not only the four World Wars but the 22nd century Dalek invasion. (AUDIO: Frostfire)

Around this time, an Earth expedition led by Professor Parry was trying to uncover the lost tombs of the Cybermen on Telos. There they discovered that the Cybermen, contrary to popular belief, had not gone extinct, but instead gone into frozen hibernation in their huge underground tombs. One of the members of that expedition, Eric Klieg along with his accomplice Kaftan, aimed to use the Cybermen's strength, coupled with their intelligence from the Brotherhood of Logicians would transform the Earth Empire into a new power. His plan fell apart and eventually the tombs were sealed shut, supposedly forever. (TV:  The Tomb of the Cybermen)

Some other cultural tidbits of the 25th century included:
 * The Beatles were considered "classical music", and a memorial theatre dedicated to them existed in Liverpool. (TV: The Chase)
 * Aspirin tablets were no longer in common use. (TV: The Web Planet)
 * Humanity travelled in hyperspace. Such journeys were common and commercial. (PROSE: Judgement of the Judoon)
 * Fringe archaeologists considered a H. P. Lovecraft story from 1936 to be based on a true story. (PROSE: The Taking of Planet 5)

The Doctor once encountered a Stigorax in Birmingham in the 25th century. (TV: The Happiness Patrol)

After arriving in London in 2167, the First Doctor, yet to determine at which point in time they were, told Ian Chesterson and Barbara Wright to bear in mind that they might have landed in the early 1900s or the 25th century. (TV: The Dalek Invasion of Earth)

By this time, pandas were extinct. (PROSE: The Eleventh Tiger)

The snowy planet of Isen VI was terraformed into a tropical paradise by Kano Dollar for the warrior princess Thanna. Within three years, the terraforming had inadvertently caused global disaster caused by the long-lost Hyperion Rann-Korr. With the help of the Twelfth Doctor and Clara Oswald, Rann-Korr was frozen within the planet's Aurora ocean. (COMIC: Terrorformer)

The 25th century was notable for hosting the life of Darzil Carlisle, initally described by the Fifth Doctor as one of the most eminent advocates for peace in human history. Born outside Olympus Mons on Mars in 2414, Darzil Carlisle was later relocated to an orphanage in Finchley, north London, at the age of three following a freak airlock accident which killed his parents. In the 2430s, the 17 year old Darzil Carlisle earned a scholarship to the Phobos Academy of Music, proceeding to study for three years before, as quoted by the Doctor, "stumbling into a glorious career as a peace negociator", in which he was apparently responsible for ending 36 wars. However, the Doctor, following an encounter with an older Darzil Carlisle in the later period of the century, would realise that Darzil's career was actually the result of him having taken the credit for actions that he would perform in his personal future. (AUDIO: The Game)

In the mid-25th century, it was illegal for a human to sleep with a non-human. (PROSE: Dead Romance)

Alternate timeline
In a potential history shown by the Eleventh Doctor to Jean-Luc Picard, the Cybermen, having integrated both the Doctor's N-Space and Picard's parallel universe before conquering the Borg Collective, continued the campaign to convert the galaxy. Among the races converted en masse during this century were the Klingons by 2418, the Raxacoricofallapatorians by 2448, the Vulcans by 2468, and the Judoon by 2493. (COMIC: Assimilation²)