Equestria Time (MLP Timeline)

How the hell does time work in Equestria?
 
Seconds, Minutes, Hours, Days, Weeks, and Years are all directly referenced. There’s no evidence for it, but I think it’s safe to assume that generally speaking their time works on the same rules. 60 seconds = 1 Minute. 60 minutes = 1 hour. 24 hours = 1 day. Pony Calendars are also shown, so they do seem to operate on months as well.
 
After that, though, it’s kind of hard to figure out. Some episodes say “years”, and others refer to “moons.” The “Moons” one really throws me through a loop. It doesn’t appear as though Equestria’s moon goes through phases (not that I can tell at least) and if it did, you can’t tell how it goes. Equestria Girls implies that 30 moons is a really long time, however Granny Smith says that the Apple Family Reunion is held once every 100 moons, which can’t be THAT long considering they held two reunions between the pilot and Twilight’s Ascension.
 
Though if you ignore the Moons concept, it’d be easy to discern that only a year or two have passed since Twilight first moved to Ponyville. It’s mostly discerned from the episodes in Season Five like Princess Twilight (Celestia’s comment on being able to enjoy the Summer Sun Celebration implies it’s the first one since Nightmare Moon’s defeat) and Tanks for the Memories (Dash’s first Winter after getting Tank).
 
Thoughts?

@Gemstone
 
They’re using “moons” exactly because it’s such a vague and unclear unit that it could mean almost anything. :)
 
However, I tend to think it’s basically equivalent to “month”. In that case, the thirty-moon cycle of the portal mirror in Equestria Girls is close to three years, which while not a huge length of time, is certainly a long time to spend trapped in a strange world away from your home and friends.
 
Going by the “moon” = “month” equivalency, the Apple family reunions would then be eight and one-third of a year apart, which makes sense; that way, Applebloom would have been very young during the last one, and Applejack and Big Mac would have been children or young teens at most. That way, AJ would certainly have memories of the previous reunion, but wouldn’t really have been involved in planning and organizing it.
 
Finally, and this is my pet peeve, nothing in the show actually suggests a radically compacted timescale where S1 to S5, or just S1-3, take place in just a year or two. The comment by Celestia that people keep referring to does not actually say that it’s the first SSC after Nightmare Moon’s defeat, merely that it’s the first where Luna is participating. The various seasonal and holiday episodes over the seasons suggest that at least a couple of years pass between Twilight’s arrival in Ponyville and her ascension at the end of S3. (It’s notable that pretty much nobody suggested such a short timeline before Princess Twilight!) “One season” = “approximately one year in the setting” is my preferred rate, but I admit there are good arguments to be made for a shorter timeline. Not so short as just one or two years, however! (If nothing else, it would be absurdly eventual year or two; the fandom makes a lot of jokes about life in Ponyville having turned much too interesting ever since Twilight moved in, but there’s a limit to everything. ;) )
 
As for Tanks for the Memories, it doesn’t really fit into any coherent chronology you might make, if only because there already was a winter episode after “May the Best Pet Win”. And it doesn’t quite make sense as an out-of-order episode transplanted out of S2 either, because of the character development both Dash and especially Fluttershy show. It’s a good episode, but it really is an anachronism. :)

@Lurks-no-More  
Considering S4 started repeating “annual events” from the previous seasons (both in actual focus and in throwaway dialogue), I’d say they did intend at that point that only a year had passed. That being said that doesn’t entirely jive with dialogue here and there in the earlier seasons, suggesting this wasn’t always the plan. But your “year a season” doesn’t work for stuff like the CMC - or more glaringly, the Cake twins. Note also that most annual events in the series have only come back a second time at the most (Sisterhooves Social, the Grand Galloping Gala).
 
Hearthswarming ended up happening a third time, though, which leads me to posit (based on the series premiere being on the summer solstice) that about two and a half years have passed since the start of the show.

@Daring-Do  
I have to agree that the “season per year” thing doesn’t really mesh with character ages in the show, particularly the foals. The Cake Twins look exactly the same age in Pinkie Pride as they did at one month old in Baby Cakes, and those are two whole seasons apart. There’s also the fact that Twilight’s first Grand Galloping Gala as a princess is in Season 5, which would imply that Celestia waited an entire extra year before inviting Twilight after her ascension. Tanks for The Memories isn’t exactly the first time that the timeline has seemed iffy. Remember that Season One had Winter Wrap Up air BEFORE Twilight’s first Running of the Leaves.