My MLP Headcanons: Time-Keeping

you know, we don't really know all that much about how years work in Friendship is Magic.  some episodes suggest Equestria uses the Gregorian calendar, but aside from that, no years are ever referenced specifically.  so, here's what i like to think about how Equestria tracks years; specifically, they're tracked based on certain eras, which themselves are determined based on the current ruler of Equestria. Pony BCE: this is the period of time before the first unition of the four ponykinds (Earth, Unicorn, Pegasus, Thracian).  this covers everything from the beginning of the universe to the forming of the Ponylands city-states. Triad Era: the period of time spanning the founding of the aforementioned city-states up to the rule of Celestia and Luna in Equestria.  the first Hearth's Warming occurred during this era, as did the events of "Legends of Equestria" and the stories of the Pillars. Diurnal Era: lasting from Celestia and Luna's ascension to the throne all the way to the banishment of Nightmare Moon.  Discord's (and Cosmos') reign of chaos occurred within this era, as well as the loss of the Crystal Empire and the arrival of Tirek and Scorpan. Celestial Era: this is the era in which Friendship is Magic takes place, covering the time from Nightmare Moon's banishment to the ascension of Twilight Sparkle.  i assume you know what happened during this era.  :P Twilight Era: the oddly poetic name for the era starting with Twilight's ascension and ending with the loss of magic and the sealing away of Equestria.  Luster Dawn's offscreen adventures happened during this era, as well as the battle against Opaline and the hibernation of the dragons. Separation Era: the era in which G5 takes place, and the second-longest era after Pony BCE.  this begun with the separation of the ponykinds after the loss of magic and continues to this day. each era aside from Pony BCE starts counting years from 1.  for instance, Nightmare Moon was released in the year 1000 of the Celestial Era, and the show ended in the early 1000s.