The Nephites kept track of time from the following reference points:
- Years were counted from the time Lehi left Jerusalem, in about 600 B.C.
- Time was measured from the commencement of the reign of the judges, in about 91 B.C.
- Time was reckoned from the sign of the birth of Christ.
Source: Scriptures of the Church, Selections from the Encyclopedia of Mormonism, p. 136