At the moment this is just a very rough version of when things happened. As we come up with new events, we can add them in on an as and when bonus:

4.8 ANNM (After Nightmare Moon) – Tirek is defeated
5 ANNM – The Sirens are defeated
5.2 ANNM – The first of the magical storms hits Manehatten. Nopony is taken, and damage is minimal, but new materials are found in the wake of the storm that are not native to the planet Aedrides
5.4 ANNM – Another magical storm hits Equestria. This one emerging in Baltimare, and is far larger, the death toll quickly slipping into the hundreds. The storm does not dissipate like the first, and spills forth beasts, which only add to the confusion.
5.5 ANNM – More and more magical storms wrack the planet, no longer just limited to Equestria, but spreading across Aedrides. More creatures not native to the world come forth, pushing countries who are ill-equipped to deal with the new threats to the breaking point.
5.6 ANNM - The scale for categorizing storm sizes is finalised. The scale is christened the Nexus Chart, and stretches from one to five.
5.8 ANNM – Princess Luna takes her personal guard and attempts to reach the font of the world, the heart of magic on Aedrides. It is unknown if she succeeded or not, the last heard from the expedition coming in the form of a garbled magi-message: Arrived...of the world....Princess...answer....causalities...too many.
6 ANNM – The largest magical storm to date hits Canterlot, and is the first catagory six storm, although by todays calculations it is closer to a Cat eight. The entire city is destroyed, reduced to what is now the Great Wasteland. Before its destruction, Celestia was confirmed as being amongst the dead, while Blueblood activated Starfall Protocol, allowing the control of the sun to pass back to the unicorns. It is unknown what happened to Prince Blueblood or the majority of the Equestrian Guard. Canterlot ceases to exist in the cinventional state, becoming what is known as 'The Great Wasteland'.
6.1 ANNM - A storm almost identical in size to the storm that hit Canterlot weeks earlier opens up over Manehatten. The entire city is reduced to rubble, with all manner of beasts prowling the ruins. While the casualty list is huge, the biggest blow by far is the loss of Captain Spitfire of the Wonderbolts and Captain Nightshade of the Shadowbolts. Command of these two elite units passes on to Lieutenant Soarin and Lieutenant Stratus.
6.2 ANNM – Equestria’s military finally collapses, unable to bear the losses anymore, with hundreds, if not thousands of poniesdeserting their posts to be with their loved ones. The countries government quickly follows, the remaining cities and towns fortifying themselves to better defend their own borders. The other countries soon fall to similar fates, allowing opportunists to carve out huge swathes of power for themselves. Many believe that this is the end of days.
6.4 ANNM – The magical storms begin to finally fade.
8 ANNM – The first of those now referred to as travellers return to Equestria.
14 ANNM – Prince Blueblood and his crew return to Equestria
14 ANNM - Rumors begin to spring up about a lavender unicorn reappearing in the Everfree Forest. Although no one has actually confirmed the rumor, it is believed to be Twilight Sparkle.
15.5 ANNM - Pinkie Pie returns to Equestria
16 ANNM - Darth Spectra and Gilda return to Equestria
16 ANNM – Present Day

4124346 16 ANNM - Darth Spectra and Gilda return

4124351
Updated and added in

4124377 Alright.

4124346

From conversations, I'm fairly sure Twilight is supposed to return around 13ANNM, while Spitfire and co show up in 16ANNM, not sure when Pinkie's supposed to reappear, though apparently it's where Spitfire and co vanished from.

Also, 6ANNM, roughly a week after Blueblood vanishes is when two storms hit Manehatten in succession, the second of which vanishes both Wonderbolt and Shadowbolt Captains along with a militia pony and three civvies. Both named units have their command devolve to the next in line, namely Soarin' and Stratus if no-one claims them.

Twilight return about 13-15 ANNM because she lives in the everfree forest now and nopony know she has actually returned.

4124346
15.5 ANNM - Pinkie Pie returns

4124346
Add twilight at 14ANNM but she probably in tje story wint be found by other ponys till 16-17ANNM bit still be in eqistria before that.

4146871

16PNNM is the most likely period for things to be found out about her, since my group will be setting up in Ponyville and will be doing bounties, hunting and foraging in the Everfree, though rumours are probably going to be around the towns in that area, so Ponyville and Cloudsdale primarily.

Also, 4124346

6.1 - Double storm in Manehatten, pretty much destroys the place and warps out Spitfire, Nightshade, Sparkler, Lemon Hearts, Roseluck and Lily Valley

16 - Dforgrym squad Sealgair Gailleann appears in Cloudsdale's Colosseum (said squad is the group that were taken from Manehatten + Jacinth, J'kreth, Civa and C'ret)

4146871
4147168
Done on both accounts. The story will start in 16 ANNM, so that will be when Spitfire and Co probably end up looking into reports about a metal beast, instead finding Blueblood and The Good Prince, Dash and Gilda will probably try to hunt them as they are worthy foes, but will eventually see that they need to work together, and then they can go and try to find Twilight, since they believe the rumors about her being back are true.

This is all my idea of course, if the owners of said characters want to change stuff, then they can of course do so, I'm just making an example.

4149572

I've been going more along the lines of there being rumours of the AT-TE and Twilight (not that she's named) being picked up in Berry's bar in Ponyville (presuming she's one that didn't get warped or killed at the moment) and they start poking into things a bit before heading off to deal with an undead infestation in another town en route to checking on a 'ghost town' that's that way due to a number of vrondi being warped there and carrying out their last orders, meaning watch for magicals and report to the nearest Herald preferably a Herald Mage. Of course this being Aedrides rather than Velgarth there's a huge number of magicals and a derth of Heralds so they've just been glaring at everyone in the town and creeping out the majority of them.

Also got some plans to bring in the remaining higher ups among the Wonderbolts and Shadowbolts for 'quest' purposes, which will probably lead to things getting noisy in Cloudsdale, along with talks with Daisy and Sparkler and Lemon Hearts families eventually. Thinking maybe Sparkler's family being held somewhere, resulting in more nastiness, though I might interweave things since I've only got rough ideas.