Distant past

The distant past was that period which was historically remote to the Doctor's usual travels. It had no exact date range, but could be considered to extend from the Big Bang (and perhaps earlier) to the development of modern humans, in about 100,000 BC. The Dark Times of the universe were known to have occurred in the distant past.

Beginning of the universe
At the beginning of time, the Big Bang occurred due to a combination of at least two events: an ejection of fuel from the leper ship Terminus (TV: Terminus) and the explosion of the time ship Vipod Mor. (AUDIO: Slipback) This occured on Febuary 13, 13,500,017,093 BC, at 11 am. (PROSE: Time Traveller's Diary) Although one source suggests the Universe to be older than 50 billion years old (AUDIO: The Nowhere Place). The TARDIS attempted to return to this point in time, which was also known as Event One, only to be prevented from doing so. (TV: Castrovalva) The first stars and planets were formed in the aftermath of the explosion. Life evolved and civilisations arose on many worlds. (PROSE: Timewyrm: Apocalypse, Falls the Shadow)

On Planet One, the oldest planet in the universe, River Song carved a message for the Doctor in a diamond cliff. (TV: The Pandorica Opens)

Virus 7001B, one of millions of viruses released from the Amethyst Viral Containment Station in the far future, was sent back to time to the beginning of the universe and resulted in the creation of life itself. (AUDIO: The Viyran Solution)

The Grey Man's race observed as the first humanoid race destroyed themselves in bacteriological warfare. In response, the Grey Man created Cathedral to introduce uncertainty to the concept of duality which his people had imposed on the universe. (PROSE: Falls the Shadow)

The Shadow claimed to have waited for the Key to Time "since eternity began". (TV: The Armageddon Factor)

Billions of years BC
According to one account, the first sentient race to evolve on Earth was active circa 50,000,000,000 BC, wherein they accidentally erased themselves from history during a time travel experiment, which flung their species to 'Time's End'. (AUDIO: The Nowhere Place)

According to one account, the year 10,000,000,000 BC was at the "dawn of human civili[s]ation". During this time, the Eleventh Doctor accidentally started a galactic space-war that changed the course of human history every time something blew up. This caused radical changes in the 21st century, such as humans changing species before the timeline was set right again. (COMIC: Short-Change)

According to another account, the Earth formed in the solar system around 6,000,000,000 BC. The Eleventh Doctor photographed what would be the site of the Caliburn House as part of his investigation of the Caliburn Ghost. (TV: Hide) However, the Tenth Doctor claimed he went back "4.6 billion years" from 2007 at a point to when there was "no solar system. Not yet." The Doctor and Donna Noble saw the Secret Heart, a Racnoss spaceship hiding from a war and entering what would become the solar system as the Earth began forming around it. (TV: The Runaway Bride) At the same time, the Sentience was trapped inside the forming Earth, underneath the area that would later be known as Crook Marsham. (PROSE: Nightshade) According to one account, the Moon left the Cthalctose homeworld around 6,000,000,000 BC and eventually entered the solar system. (PROSE: Eternity Weeps)

Around 5,000,000,000 BC, the Arkive were created to preserve the knowledge of their creators after the creators' planet was destroyed by a supernova. The plan failed and the Arkive was badly damaged by the supernova. Eventually, it drifted into the solar system and became the core of Mnemosyne. (PROSE: The Wheel of Ice)

Around 4,500,000,000 BC, the Fourth Doctor and Sarah Jane Smith observed Earth's development over the course of several million years and encountered Megron. (AUDIO: Exploration Earth)

Billions of years BC, the seas on Androzani Minor dried up. (TV: The Caves of Androzani)

Around 3,000,000,000 BC, a civilisation of Venusian thrived on Venus. (PROSE: Venusian Lullaby)

Around 1,000,000,000 BC, the Khorlthochloi committed a near genocide against the Valethske (PROSE: Superior Beings) and invaded Earth shortly before their extinction. (PROSE: Synthespians™)

Hundreds of millions of years BC
Around 1,000,000,000 to 500,000,000 BC, the Angels created the bases on Belial and Moloch. They then used the "Mushroom Farm" (which could modify morphic fields) to change their shape. (PROSE: Lucifer Rising)
 * A more precise date can't be given, since this was gleaned from archaeological research and the living Angels refused to communicate with the humans.

Around 500,000,000 BC, the Cirranin home planet was destroyed in a war, wiping them out. (PROSE: The Last Dodo)

According to one account, life developed on the Earth around 450,000,000 BC when the Archaeons seeded it and carefully controlled life from their vivariums. This account claimed that the Moon was already orbiting the Earth. There, the Archaeons were carefully nurturing the early forms of life before they disappeared when they were trapped inside a stasis field. (AUDIO: The Beginning) According to another account, the last Jagaroth ship exploded on primitive Earth around 400,000,000 BC. The explosion killed the crew and splintered Scaroth into 12 sections in human history. The explosion also caused the development of life on Earth, meaning that to prevent the explosion would have left the planet a desolate rock. (TV: City of Death)

Around 260,000,000 BC, the Permians evolved on Earth. They eventually wiped out 96% of life on the planet and went dormant. (AUDIO: The Land of the Dead)

The Silurians and Sea Devils developed an advanced culture, but were forced underground due to the arrival of the Moon. (TV: Doctor Who and the Silurians)
 * This era has never been consistently dated.

Around 150,000,000 BC, the Millennium War occurred, causing massive amounts of death and carnage. (PROSE: The Quantum Archangel) Also around this time, a civil war erupted on Kastria, which led to the destruction of Eldrad and the eventual extinction of the Kastrians. (TV: The Hand of Fear) A planet inhabited by parasitic lifeforms was destroyed by its dying star. One individual was able to escape, but crashed on Earth in the Mariana Trench. (AUDIO: Submission)

Around 140,000,000 BC, the Vardon-Kosnax War occurred, devastating Xeriphas. As a result, the Xeraphin merged into a gestalt and transported themselves to Earth. (TV: Time-Flight)

Around 100,000,000 BC, an allohistorical lure, sent back in time by Arkive, landed on Earth. It killed a dinosaur and was fossilised with it. (PROSE: The Wheel of Ice)

According to the Twelfth Doctor, around 100,000,000 before the 21st century, the Moon entered orbit around the Earth. (TV: Kill the Moon)

Tens of millions of years BC
The Seventh Doctor dropped off Ace on Earth during the Cretaceous period. (COMIC: Train-Flight) After arriving to pick her up around 75 million years BC, he witnessed her lead the dinosaurs in destroying an alien colony being constructed by slave labour. (PROSE: Living in the Past)

65 million years BC, the crash of a human freighter from the future caused the extinction of the dinosaurs. (TV: Earthshock) In the immediate aftermath of the event, Jack Harkness, who was present on Earth, lived off of dinosaur meat. (TV: Fragments) Adric, who was on board the freighter, survived and used the alien computer on the ship to create a city of intelligent scorpions, which he ruled over for five hundred years until he was reunited with the Fifth Doctor and Nyssa. (AUDIO: The Boy That Time Forgot)

The Cardiff Space-Time Rift connected the Palaeocene ocean and the Cardiff Bay in 2008. The amino-acids from the Palaeocene broke down pollutants like oil, improving the quality of sea-water. (PROSE: The Undertaker's Gift)

Around 60 million BC, a Xylok ship crashed into Earth and became trapped in the crust. (TV: The Lost Boy)

Around 50 million BC, Arkive tried to attract the Silurians to rescue itself. The attempt failed and the rings of Saturn were created by the destruction of Mnemosyne. (PROSE: The Wheel of Ice) Also around this time, the Eighth Doctor and Bernice Summerfield were briefly transported into Epsilon Minima's past. (AUDIO: Benny's Story)

Around 20 million BC, the Tendurek Formation was created on Earth as part of the Genesis of Cthalctose. (PROSE: Eternity Weeps) Around the same time, the creodont went extinct. (AUDIO: False Gods)

Around 15 million BC, a number of stones were carved with organic-looking reliefs that seemed to move when viewed. The Seventh Doctor found some of them in a museum in 1915 Haiti. (PROSE: White Darkness)

Around 12 million BC, the Fendahl teleported itself to Earth from its homeworld using psychic power. (TV: Image of the Fendahl) Owls evolved on Earth. (PROSE: Just War)

Millions of years BC
Millions of years BC, the Mastons went extinct when their planet was destroyed. (AUDIO: Slipback)

Millions of years BC, the Hervoken went to war with the Carrionites. (PROSE: Forever Autumn)

Around 5 million BC, the Xhinn were created out of fire in an alternate universe. They rebelled against this creator and were banished into the universe the Doctor resided in. (PROSE: Amorality Tale)

Around 2.5 million to 3.6 million BC, the Tractite attempted to meddle in humanity's prehistory. (PROSE: Genocide)

Around 1 million BC, the Hoothi began preparations on Heaven for a new attack on the Time Lords. (PROSE: Love and War)

Hundreds of thousands of years BC
In 497,400 BC, Saraani civilisation developed. (PROSE: Dry Pilgrimage)

Around 250,000 BC, the Monks of Felsecar began preserving the most dangerous objects and information in the universe. (PROSE: Love and War)