ÆRA. The point of time from whence any number of years is begun to be counted, is called a period, era, or epoch. The word era comes from the Latin æra, because the Romans marked their years with a kind of small brass nails. The difference between the terms era and epoch is, that the æras are certain points fixed by some people, or nation; and the epochs are points fixed by chronologists and historians. The idea of an era comprehends also a certain succession of years proceeding from a fixed point of time, and the epoch is that point itself. Thus the Christian era began at the epoch of the birth of Jesus Christ *.