https://www.fimfiction.net/story/418440/those-forty-years (The sequel is out! Check it out here. Check out my latest blog for why it's on my co-author's profile instead of this one.)

A legendary magical discovery leads the protagonist Twilight Sparkle through a chain of events that not only explain Celestia and Luna's history, but a history about herself that even she could not have imagined.
Co-Author profile link.

WE HAVE COVER ART! 8/3/2016 Check the source for the artist. (permission was given)

Mark always knew he was... well, you know. But what was he supposed to do about it? Nothing, really. It didn't matter anyway. Nothing was ever going to change. Or so he thought, until a portal to Equestria appeared in his house. But with that portal, he'll be forced to acknowledge and confront what he is head on.

Preread by everyone's favorite writer, Starscribe. They've helped make this story ten million times better than it was before.

Cover art by CrimsonWolf360. You can find their work here.

I have no idea what happened. One second, I'm sitting at my desk, working. The next second, I'm Sombra. Or rather, I'm in his body. And nobody seems to believe me about it...

Now with (amazing!) cover art by Mix Up. You can find their work here.

Time is a neutral party. It takes no sides, only proceeding without a care for those caught in its trap. That is how it should be...
But not all traps are foolproof.

When a pony seeking the Night Princess's counsel intervenes during an assassination attempt, Luna knew there was more to this stallion than met the eye.
However, even her expectations had limits. That, Luna discovered, was a mistake.

One question troubles her thoughts as a new problem presents itself in the form of this stallion; how does a heart and mind cope when one escapes the trap of time? What happens to a good heart when it is worn away, year after year, all stemming from a single mistake, no matter how good the intentions?

Equestria Daily seal of approval: https://www.equestriadaily.com/2019/11/fanfiction-timeless.html

Takes place during/after Season 9.
Sequel: Sunspots

In the beginning, The Great Weaver brought together the world, from the mountains to the forests. Stitching it together, the Great Tapestry connects all living and nonliving things.

The Changelings found themselves especially connected to this Tapestry. Legend says that the first Changelings fell through the world as it was woven together, only to be caught on the First Weave beneath it all.

But what happens when something else is caught in the Weave?

Prince Phasmatodea, son of Queen Chrysalis, remembers what it was like before he hatched. He remembers being a human. He remembers dying. And he fully intends on avoiding another death.

But being gifted a new life does not matter when one failure, one false step, will lead to your untimely demise in the Changeling hive, for Prince Phasma must survive his toughest adversary from the start: Mother Dearest.

Cover art as of 1/18/21 by Nixworld

Rainbow Dash's morning was pretty much ruined.
She tripped getting out of bed and landed flat on her face, giving herself an aching muzzle.
She forgot to buy her favorite brand of hay flakes at the store yesterday and had to eat plain toast for breakfast.
She found out she had to pull double-duty today and tomorrow on the weather patrol.
Oh, and she found a nearly-dead foal, broken and bleeding at the edge of Ponyville.

The rest of her day became a whirlpool of stress and worry but the colt woke up, thank Celestia.
Something's not right, though. Nopony can find his parents, he's not in the registers, and there's an unsettling look in his eye...

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YouTube reading by Fire Hearth

Chinese Translation by forgivenlove

Russian Translation by Likantrop

TV Tropes page, if you're interested in that sort of thing.

When I agreed to be sent to Equestria I didn't read the fine print. I'm the wrong age, the wrong sex, and lost in the wilderness.

New Cover art commissioned from Lunar Froxy.