A thousand year absence from the world would be disorienting for anyone, but when your job is Head of State, understanding how society has changed during your interregnum is vital. Princess Luna, banished in the age of the longboat and the longbow, has returned just in time for the launch of the tablet computer. With the help of her sister, she undertakes to understand the history she's missed and the people she finds herself among, in order to resume the duties of her title.
This story takes the form of a series of conversations between Celestia and Luna that take place months and years apart. It is openly concerned with political ideas and how societies are organised, and not at all concerned with monsters and magic beyond the conceit of immortal monarchs. The Alternate Universe tag is there because I will be ignoring every single one of the thousand year catastrophes that occur in the show after the Nightmare Moon crisis, the retirement of the Princesses, probably the presence of any other Princesses, and anything else in the show I feel like ignoring, because I find them irrelevant to the themes I want to cover.
In short, if you wanted The Audience with ponies, I got you covered.
This story can be considered canon to my comic works such as The Sunjackers, and my other associated worldbuilding projects, and uses the same date system as them (ie. roughly matching our own, with the return of Nightmare Moon happening the same year as the episode aired, 2010). May also be your jam if you like Equestria At War, but not affiliated at all.