The first day of the week, named for the sun in a number of languages because it coincided with the day dedicated to the sun in the astrological week that was popular in the Roman Empire. This planetary week rose from the Hellenistic astrological practice of assigning each hour of the day to one of the seven planetary gods (the “planets” being the five visible to the naked eye, and the sun and moon) and of naming each day for the god who was supposed to preside over the first hour of the day. The system came from the Greco-Babylonian astrology that developed after the conquest of the East by Alexander the Great. The hours were assigned to the planets in the following order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Thus the Day of the Sun ended, according to this sequence, with...

From the Seventh-day Adventist Encyclopedia. Published with permission from the Review and Herald Publishing Association.