The Chinese eras or Nian Hao were used sporadically from 156 BC and continuously from 140 BC.
Until 1367 AD several were used during each emperor's reign.
If it lasted the entire length of the leader's reign, then that leader is often referred to by that name posthumously.
However, the leader was often given a more complex formal posthumous name as well.
It could last from one year to the length of the leader's reign.
If it lasted more than one year, numbers were appended to the era name.
It should not be confused with a temple name, by which many leaders are known.