ttps://en.wikipedia.org/wiki/Mandate_of_Heaven" target="_blank">"mandate of heaven"</a> political doctrine. The epochs were chosen carefully to coincide with significant political events at the expense of reducing the discrepancies between the calendrical and astronomical conjunctions. For example, epoch A was in the year <span class="nowrap">N<sub>-360</sub></span>, which coincided with the year when Duke Xiao of Qin (秦孝公) became the ruler of the Qin state. During his reign, Duke Xiao employed the le