Often there would be no indication of exactly when the reference event took place. If an eclipse was described in the record of events , it could be compared with actual eclipses that were known to have happened near the time and place in question. If there were only one eclipse that fit the description, then the dates could be fixed with certainty. Many historical chronologies have been verified or compared using this method. The earliest record of a solar eclipse comes from ancient China.
Historians know the account was written sometime within a period of about two hundred years.
During that time there were several total eclipses visible in China. The 2134 B.C. eclipse is simply the best guess. The story goes that the two royal astronomers, Hsi and Ho, had neglected their duties and failed to predict the event. Widespread Oriental belief held that an eclipse was caused by an invisible dragon devouring the Sun. When this eclipse took place, the emperor was caught unprepared.