Where Do the Days of the Week Get Their Names?
The days of the week were named after the sun and moon, and for ancient gods and goddesses. The Romans named Sunday and Monday for the sun and moon. Tuesday, Wednesday, Thursday and Friday were all named for deities in Norse mythology.
Tuesday is the day of Tiw, the Norse god of war; Wednesday is “Woden’s day” for Woden (Odin), the supreme Norse god. Thursday is named for Thor, the thunder god, and Friday comes from “Frigg’s day” for Frigg, the goddess of love (and Odin’s wife and Thor’s mother). Saturday is named for the Roman god Saturn.
In some other languages, the days are named for corresponding deities of the regional culture, either beginning with Sunday or with Monday. In the international standard ISO 8601, Monday is treated as the first day of the week.
Between the 1st and 3rd centuries the Roman Empire gradually replaced the eight-day Roman nundinal cycle with the seven-day week. Our earliest evidence for this new system is a Pompeiian graffito referring to the 6th February (viii idus Februarius) of the year AD 60 as dies solis (“Sunday”).
Another early witness is a reference to a lost treatise by Plutarch, written in about AD 100, which addressed the question of Why are the days named after the planets reckoned in a different order from the actual order?
The days were named after the planets, in the order Sun, Moon, Mars (Ares), Mercury (Hermes), Jupiter (Zeus), Venus (Aphrodite) and Saturn (Cronos).
The seven-day week spread throughout the Roman Empire in Late Antiquity. By the 4th century, it was in wide use throughout the Empire, and it had also reached India and China.