A thousand years ago, the Crystal Empire was banished to another plane of reality, frozen in time. With its disappearance, many lives were affected and changed. Time in the Empire has now resumed, returning in sync with the rest of Equestria.
A year has come and gone since its return. Much and little has transpired since it vanished into thin air, and the clock is ticking once again for it's denizens. However, not all scars have mended. Many lives are now intertwined in ways unseen by the naked eye, but they stand the test of time.
The Alternate Universe tag is only present because the history is only slightly altered (a characters reasoning for taking a particular path)
Disclaimer: I do not own My Little Pony: Friendship is Magic or any images shown, stories, or songs referenced.