Two weeks before the 1000th Summer Sun Celebration, Moondancer discovers a forgotten spell scrawled across the pages of an ancient book. Casting it threatens to turns her world upside down: faced with glimpses of an Equestria contradicted by historians, she must use all of her intellect to piece together the mystery surrounding Mage Meadowbrook, Princess Celestia, and the mare with the mane of stars—before the project destroys everything she's worked for.

It's a good thing she can rely on Twilight Sparkle for help.

Spanish Translation from Spaniard Kiwi!

Twilight still isn't having a very good day. An army of changelings is attacking Canterlot, and the experimental spell that blew up in her face has stuck her in a time loop until she gets everything perfect and saves Equestria.

She's got a plan. She's also got a problem: Suddenly, she's not the only one whose day is repeating. And when you're caught between unstoppable force and immovable object, life has a tendency to get complicated.

* * *

This story is an authorized alternate-universe re-imagining of Eakin's Hard Reset, in which multiple loopers turn the time shenanigans up to 11. (Knowledge of Hard Reset is not required, but based on reader comments, will help in sorting out the early chapters.)

Cliff's Notes versions: RampantArcana has started a GitHub repository to codify the time-loop rules and the early-story timeline. Hawthornbunny has posted a chapter-by-chapter breakdown of all the loops, including the ones we don't see, with a lot of critical analysis. Those links contain spoilers (of currently posted chapters). If you're confused, either one of those fan projects is a great starting point, and story comments have a lot of insightful discussion as well.

Publication schedule: 2014 kicked my plot, but as of November I'm picking up the writing again and hope to have something by the end of the month.

Cover art by Alexstrazsa.

The princesses gave their magic to Twilight to prevent Tirek from stealing it. As a result, they end up stuck in Tartarus.

Marvelous place, Tartarus. Really brings ponies together. The fact that things manage to go downhill here says a lot about the wonders of family and alicornhood.

Spanish translation by SPANIARD KIWI

Audio Drama by Espa_Roba_5 and Ajvasquezbrony28
Live reading by The Living Library
Live reading by Astro-Brony

Proofread by Octavia Harmony

Ponyville has a problem: Twilight's friends all switched Cutie Marks, and the musical numbers are flying thick and fast.
Lyra has a problem: She can't handle the way musical numbers get into your head and take you over.
Bon Bon has a problem with that.

(Pony Fiction Vaulted • Featured on EqD)

Reviews and other word-of-mouth:
"I just can't find words for how much I enjoy the ideas on display here. … I didn't expect to be rating something this highly, this quickly." –Bradel
"The Lotus Eaters was the story that made me realize horizon wasn't just good, he was really good. Then Fugue State showed me he was really good repeatedly." –Bad Horse
"a strange but intriguing story ... [horizon's] so good at this ponyfic lark that it's still a highly satisfying read. ★★★★" - Louder Yay
"This story is weird, and I mean that in a good way. … [Horizon] thought about how ponies might react if [musical numbers] were a constant in Equestrian life." –Chris

Fugue State now has a sequel!

In which Shining Armor receives a promotion, Princess Cadance reunites with an old friend, and cloudfall is finally made. Part of the "Cadance of Cloudsdale" cycle, now with its own group!

This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169

When Rarity is overwhelmed with making designs for an agriculture exhibition, she turns to Applejack for advice. But when she gives Applejack a hair style treatment in return, the apple farmer lets her accent slip from southern drawl to sophisticated Manehattenite. The result? More fancy parties than you can shake a candy apple at!

Three missing pieces, two loving alicorns, and a single stupid decision that will set young Princess Cadence on a fresh new course. Story One of the "Cadance of Cloudsdale" cycle.

Cadance of Cloudsdale (so far!) is serialized in Spanish! See here for the Spanish translation courtesy of SPANIARD KIWI!