With Alexander’s conquest of Babylon, the Greek world adopted the seven-day week, based on the visible planets and named for associated deities.
Babylonian: Shamash, Sin, Nergal, Nabu, Marduk, Ishtar, Ninurta
Greek: Helios, Kallisto, Ares, Hermes, Zeus, Aphrodite, Kronos
Roman: Sol, Luna, Mars, Mercurius, Jupiter, Venus, Saturnus
Nordic: Sun, Moon, Tiw, Wodin, Thor, Freya, Saturn
Modern: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday