For starters, let's set up the Solar System.
Timeline
All dates will be in Earth years.
>150,000 BC: Twilight Sparkle, and the rest of the Elements of Harmony, pass away. Princesses Celestia and Luna send their souls into space, forever free.
1957 AD: The Soviet Union launches Sputnik 1, the first ever manmade satellite; proving that space exploration is possible outside of science fiction.
1959 AD: The Vietnam War starts. The United Nations and the Soviet Bloc are at war.
1969 AD: America lands Apollo 11 on the Moon. The first step into human space exploration.
1975 AD: The Vietnam War ends. North and South Vietnam are united under the Socialist banner.
1976 AD: The first Space Shuttle; the Enterprise is built. A huge leap into human space exploration
1998 AD: The beginning of the construction of the International Space Station; Princesses Celestia and Luna pass away, along with the rest of known Equestrian civilisation. Some ponies fled to distant stars, establishing their own race and culture. Old Equestrian history is lost forever.
2011 AD: The Space Shuttle program is shut down; the last Shuttle Atlantis concluding the Program with its last flight, STS-135.
2065 AD: The first human-applicable cryogenics technology is manufactured in London, England.
2071 AD: Gamma/Nuclear propulsion technology is mastered, proving results massively better than its predecessor; Helium-3.
2142 AD: The United Nations build the Barack Obama Memorial Space Station at Relay Point 7 near Jupiter, increasing the maximum distance one ship can travel. This method, known now as the checkpoint system is used to colonise hundreds of worlds.
2154 AD: Humanity reaches the Perseus Belt of the Milky Way galaxy, finding a dead planet containing the ruins of a mountainside castle. Several fossils of miniature equines is found on the planet, dubbed P3X-481. The tomb and skeletal remains of a ruling figure is found. The ruling figure's skeleton has the proportions of an Arabic Horse, except for the stunted muzzle, and larger eye sockets. Ancient banners with a sun-like motif are found in the tomb, as well.
2267: Humanity colonises half of the entire galaxy, finding allies amongst the Krr'vaah, a quadrupedal race of insect-like creatures who communicate with advanced mathematics via sonar. Herald Smithsonian finds a rogue electromagnetic pulse seemingly roaming around space. He attempts to scan it, and the ship he serves in, the UNS Sol's, systems go haywire.