Prior to the Meiji period, era names were decided by court officials and were subjected to frequent change. A new era name was usually proclaimed within a year or two after the ascension of a new emperor. A new era name was also often designated on the first, fifth and 58th years of the sexagenary cycle, because they were inauspicious years in Onmyōdō. These three years are respectively known as ', ', and ', and collectively known as '. Era names were also changed due to other felicitous events or natural disasters.