The Church of Solstice recorded and categorized Equestrian history into rough chronological sequences called "Eras". They are mainly divided by great scientific advances, though the Third Era was less an era by these standards and more so a time period Prince Solstice ordered erased.
The following are depictions of each era according to information from the original Source novel.
Contained events such as the founding of Equestria, the Saddle Arabian exodus, and the banishment of Nightmare Moon. It is only vaguely alluded to through the story. Several artifacts remain from this period, including Grandfather's Pinion, an amulet once worn by Commander Hurricane.
A long, relatively tranquil period of time beginning with the banishment of Nightmare Moon and ending with the Equestrian industrial revolution.
The Equestrian industrial revolution and the Saddle Arabian wars.
The period beginning with the Hoarfrost Apocalypse and ending with the establishment of the Church of Solstice. It is written off in Church history books as a long, brutal dark age, though Lozenge and company eventually discover it encompassed many events the Church had labored to erase from history. It even included a period of technological advancement that exceeded the Second Era.
>For the events depicted in Source: Third Era, please see the timeline on that fic's page
From two-hundred years prior to the beginning of Lozenge's story onward.