Emily Dickinson Lexicon

E'RA, n. [L. æra; Fr. ere; Sp. era. The origin of the term is not obvious.]

1. In chronology, a fixed point of time, from which any number of years is begun to be counted; as, the Christian Era. It differs from epoch in this; era is a point of time fixed by some nation or denomination of men; epo is a point fixed by historians and chronologists. The Christian era began at the epoch of the birth of Christ. Encyc.
2. A succession of years proceeding from a fixed point, or comprehended between two fixed points. The era of the Seleucides ended with the reign of Antiochus. Rollin.