The Multiversal Timeline

Note that with so many cosmic events in many separate sources, i'm going to use the Lovecraft series of events as something to have something on the page and will include many other pop culture sci fi events later down the road.

This is a full timeline comprised of all major events in interstellar pop-culture. From the Great Time War (Doctor Who) to the destruction of the Death Star (Star Wars). From man's first contact with extraterrestrials (Close Encounters of the Third Kind, Arrival, Contact) to the destruction of major planets (Titan A.E., Transformers, DC, The Hitchhiker's Guide to the Galaxy, Star Wars, etc.)

20 billion years ago

 * The time of the Silastic Armourfiends of Striterax, who build a hyper-intelligent computer called Hactar, which is later pulverized after sabotaging what the Armorfiends intended to be the ultimate weapon. It remains operative as a cloud of interstellar dust and retains the ability to subtly influence minds and matter. (The Hitchhiker's Guide to the Galaxy)

13.7 billion years ago (the Creation of the Universe)

 * A big bang occurs (general scientific belief of the universe's creation), this big bang was caused by Azathoth. A giant amalgamation of limbs, eyes, and mouths floating through space who is a cosmic deity whose very existence caused the creation of the universe (Lovecraft). Azathoth later brings three sons into existence: Nyarlathotep, the Nameless Mist, and the Darkness. As Azathoth continued creating and destroying many worlds in the universe, his sons created minions and devised a plan to put Azathoth in a sleep like state and put a halt to his chaos. They succeed and overtime, give existence to Outer gods such as Cthulhu which have the same cosmic god-like status as Azathoth and his sons. These Outer Gods then bring life to variou Great Old Ones who bring life to various alien lifeforms on other preexisting planets.

10 billion years ago

 * Influenced by Hactar, the Krikkiters evolve and achieve spaceflight. For two thousand years, the galaxy undergoes the most devastating conflict ever recorded, the Krikkit Wars, resulting in over a "grillion" casualties. After the war ends the Krikkiters' homeworld is imprisoned in a Slo-Time envelope. (The Hitchhiker's Guide to the Galaxy)

7 billion years ago

 * The First Born evolve and achieve sapience. (Babylon 5)

4.5 billion years ago (the Beginning of the Earth)

 * A race of aliens that resemble mice created a massive supercomputer to calculate and answer the questions about the meaning of life, the universe and everything. This supercomputer was named "Deep Thought" which camed up with the disappointing answer "42" as the meaning of life, the universe and everything. But based on what Deep Thought had told them, the mice-like aliens had to create a much more massive supercomputer with enough processing power to come up with a more understandable answer to their existential questions. This new supercomputer was the Earth (The Hitchhiker's Guide to the Galaxy).
 * As the Earth begin to cool down from its own creation, a Great Old One named Cthugha arrives on Earth with his legion of Fire Vampires (August Derleth).
 * The Mala'kak arrive on Earth, where they leave a single Space Jockey to consume a mutagenic, black substance that melts his body into Earth's primitive oceans. The DNA left behind by the Mala'kak is deconstructed and reconstructed in Earth's oceans where life on Earth was born. (Prometheus)

4 billion years ago (the Beginning of Life on Earth)

 * A Salaxalan ship explodes on the Earth's atmosphere, with the resulting energy released resulting in the formation of the first life forms from organic molecules scattered over the planet's primordial soups. (Dirk Gently's Holistic Detective Agency)
 * In an alternate account of the above, the ship was actually a Jagaroth ship. (Doctor Who)
 * The "Ancient Humanoids" seed the primordial soups of several inhabitable planets of DNA molecules "programmed" to evolve in certain paths, thus ensuring the future rise of several humanoid species throughout the galaxy. (Star Trek)

3 billion years ago

 * The Martian Dwarf, Setissi and Martian Glider civilizations flourish on Mars. (Doctor Omega)
 * An intelligent non-humanoid race flourishes on Venus for about three million years, before climate alterations slowly begin to mark the end of their reign. The Sou(ou)shi attempt to prey on the Venusians, but are defeated by the Doctor and physically destroyed, surviving only as a disembodied intelligence which goes dormant on primitive Earth. (Doctor Who)

2 billion years ago

 * The galaxy is ruled by the Thrintun Empire. (Known Space)

1 billion years ago

 * A race of aliens known as the Elder Things arrive on Earth in the Antarctic region and created a city within the ice. (Lovecraft)
 * The hostile species known as the Hand is imprisoned in another dimension by the First Ones. (Babylon 5)
 * Formation of the Qu civilization which would war against and exterminate the Star People over a billion years later. (All Tomorrows)

Neoproterozoic Era (1 billion - 541 million years ago)

 * 780,000,000 BC: The Chirpsithra visit the Earth and make contact with the then-dominant life form of the planet, the anaerobic lifeforms. (The Draco Tavern)
 * 600,000,000 BC: The Earth and "three other solar planets" are dominated by the mysterious Flying Polyps, a race originated from "distant universes". They would go on to fight terrible wars against the Yithian civilization which flourished on Earth much later in the Mesozoic. Some would survive hidden even into the 20th century. (The Shadow Out of Time)

Paleozoic Era (541 - 251 million years ago)

 * 500,000,000 BC: The Krell civilization flourished on Altair IV. (Forbidden Planet)
 * On Earth, the Elder Things fight against the Spawn of Cthulhu. (Lovecraft)

Mesozoic Era (251 - 66 million years ago)

 * The Great Race of Yith inhabits Earth and wars against the Flying Polyps. Meanwhile, the Elder Things are still active on the planet, now fighting against the Mi-Go as well as dealing with the first Shoggoth rebellions. (Lovecraft)
 * The Silurians and Sea Devils flourish on Earth. (Doctor Who)
 * The intelligent Voth evolve on Earth, but leave the planet en masse to escape a natural catastrophe. (Star Trek)
 * Earth is visited by aliens assuming the appearance of dinosaurs known as "Rainbow Faces" in order to blend in with the natives. (The Land Before Time VII: The Stone of Cold Fire)
 * A family of Spiders arrives on Earth during the Jurassic. (The Grim Adventures of Billy & Mandy)