BTS: Before the Story
1007: Elytra acquires his first subjects and becomes a full-fledged changeling monarch. He bears witness to Cosmos being sealed away, as well as Discord.
1007-1001: Elytra grows his power, adapts his changelings to be able to process love poison, and creates the first Husklings. Elytra vacations to Abyssinia and meets the Harborian Hive, whose queen, Harborage, teaches him the art of Heart's Artifice. Panthera is conquered in late 1001, and Harborage is rushed to the Necrosian Hive for treatment, which arrives a moment too late. The Harborians are annexed/given sanctuary by the Necrosians, eventually becoming the Necris Harborians.
1000: Elytra interferes with the fight between Celestia and Nightmare Moon, demands the Diarchs create the first "Symbol of the Two Sisters" eclipse, and seals them away, though not without striking a deal with Celestia and granting the two gifts to entertain them. The Millenial Falsity begins.
998: Elytra from the future gives Snowdrop an age crystal that keeps her young until she can reunite with Luna.
Pre-Twilight
20: Elytra sacrifices the Necrosian Trust to the Flutter Valley Sisters in an instance of The Broken Bond in exchange for Starlight Glimmer’s horn.
Before 11: The Sunset Shimmer Gala Disaster happens when Sunset throws an entire case of kanab into a fire. Elytra narrowly avoids a sexual scandal that would shake Canterlot.
11: Sunset Shimmer becomes curious about the Crystal Mirror, eventually being removed as Royal Protege and escaping to the human world with an enchanted crystal pocket mirror, thinly veiled stories of the past, and a song whose true lyrics are known by heart alone.
Immediate lead-up
Before 10: Twilight becomes Celestia’s personal student (and earns her Cutie Mark) thanks to an unexplained blast of color, which, unknown to most, has also affected five other specific ponies and allowed them to discover their Cutie Marks at the same time. The day is christened the Day of Destiny.
Alternate: The Day of Divergence happens when Rainbow Dash fails to produce the Rainboom. Twilight gives up on her dreams of attending CSGU, and Elytra and Celestia prepare contingencies for the splinter timelines that occur, mainly the Sombraverse and Changelingverse.
10 The first of Elytra’s changelings awaken.
Some point in between: Moondancer discovers Elytra and the Millenial Falsity, and is named Elytra’s regent.
3: The last of Elytra’s changelings awaken.
One month before 0: Elytra replaces the human Twilight for a week, founds the Sensors with her and Astartes, and leaves them to monitor fluctuations of Equestrian Magic.
?: Elytra and one of his changelings, Gossamer, start up music careers as earth ponies Forest Stagg and Butterfly Orchid respectively. Their music, in the groups known as the Stag Beetles and the Orchid Mantids, inspires Coloratura, and by association, Applejack finds her own appreciation for the group.
?: Elytra and Gossamer end their music careers as Forest Stagg and Butterfly Orchid by dropping their disguises while performing the Chipmunks/Chippettes’ International Music Awards mix. (Fitting, right? Born This Way, Ain’t No Stoppin’ Us Now, and Firework.) Despite the stigma, Coloratura reveres the Stag Beetles and Orchid Mantids for their willingness to just be who they really are, even if they are changelings.
?: As Celestia, Elytra confronts Chrysalis after the Fall of Trot. The encounter leaves Chrysalis and her changelings permanently scarred with holes riddling their bodies.
Season 1
0: The Millenial Falsity comes to its close. Elytra aligns the stars to break the seal on the Diarchs, and Twilight awakens the Elements. The residual magic from both Nightmare Forms mixes into a single filly, Zoravespre, who Falak adopts.
Snowdrop, the blind pegasus who created the first snowflake as a filly, finally reunites with Princess Luna. Luna is surprised to see her, but overjoyed she got to live to see Luna return.
Elytra’s Trusted subtly alter the destinies of Cozy Glow, Sunburst, Starlight Glimmer, and Tempest Shadow.
Side-plane: The Lunaverse manifests.
Cutoff point