It is originated from the day on which the Emperor Jimmu is believed to have ascended to the throne (New year's day of the 58th year of the sexagenary cycle, first day of Kanoetatsu) based on "Nihonshoki" (Chronicles of Japan).
『日本書紀』にある神武天皇が即位したとされる日（辛酉年春正月、庚辰朔）に由来している。