From 1467 to 1603, a total of sixteen eras spanned the Sengoku and Azuchi-Momoyama periods, beginning with the Ōnin era and ending with the Keichō era (which extended until 1615 in the early Edo period).  The change in the name of one era to the next was determined on the basis of consultations between the Imperial court and the Muromachi bakufu, corresponding to changes in the reign of emperors as well as war and calamities.  The changes also took account of the sexagenary cycle, a cycle of sixty terms used for reckoning time in China and the rest of the East Asian cultural sphere in these periods.