The passage of weeks shape our lives in so many ways. But the story of how we settled on seven days and the names of the days dates back thousands of years.
Why Seven Days?
The Babylonians had remarkably good astronomical knowledge. In addition to the sun and the moon, they knew about the five closest planets. Add those up and you get seven celestial bodies — one for each day of the week.
Seven days also matched the cycles of the moon — the time it took to transition from one phase to the next.
The names for the days of the week corresponded with different Babylonian gods, each associated with a planet.
- Sun: Shamash
- Moon: Sin
- Mars: Nergal
- Mercury: Nabu
- Jupiter: Marduk
- Venus: Ishtar
- Saturn: Ninurta
The Greek Gods Take Over the Week
As the Greek civilization grew to dominate the Mediterranean, they were influenced by the Babylonians. They, too, named two days after the sun and the moon, calling them day of the Sun (Hemera Helio) and day of the moon (Hemera Selenes). Hemera was the goddess who personified the day.
All the other days of the week were named for Greek gods, instead of the visible planets.
- Tuesday became hemera Areos after Ares, the merciless god of war
- Wednesday was named hemera Hermu for Hermes, the messenger for the gods
- Thursday was hemera Dios or Zeus’ day, the king of the gods and the lord of sky and thunder
- Friday was named hemera Aphrodites after Aphrodite, goddess of love
- Saturday became hemera Khronu from Kronos, the lord of the Titans, and Zeus’s father
The Romans Rename Everything
The Romans were famous for taking what someone else had done and slapping their own name on it. They simply took the Greek gods and replaced them with the Latin name.
- Tuesday became dies Martis (after Mars)
- Wednesday became dies Mercurii (after Mercury)
- Thursday became dies Jovis (after Jove, also called Jupiter)
- Friday became dies Veneris (after Venus)
- Saturday became dies Saturni (after Saturn). This was also a winter festival called Saturnalia, where enslaved people traded places with their masters for a few festive days
The Romans continued to honor the sun and the moon, making “dies Solis” (for Sunday) and “dies Lunae” (for Monday).
Same Days Different Gods
The folks living across the Rhine River had continual contact with the Romans and adopted many of their customs. When the Roman Empire collapsed, Germanic tribes spread out over Europe. They kept the same days of the week, simply swapping out their own Norse gods for the Roman counterparts.
In German, this started as sunnon-dagaz “day of the sun”. The Norse mythology called the Sun Sunna. As it migrated into English, it became Soneday.
The Germanic tribes preserved this as a moon day. The “mon” in Monday represents the Moon.
This day was named after the Norse god Tyr, a god of warriors and combat (the closest to the Roman Mars). Tyr’s name was sometimes spelled Tiw, giving us Tiwesday.
The Germanic tribes associated their chief god, Odin, with the messenger god Mercury (both traveled to earth to deliver wisdom). If it seems a strange leap from Odin to Wednesday, we need to understand he was also called Woden, giving us Wodnesday.
Just as the Romans and Greeks honored the king of the gods, the German tribes did the same, but with Thor rather than Zeus. There were two names to this day. We have the literal thunresdæg for “thunder’s day” or thorsdagr for “Thor’s day”.
This marks the biggest shift from the Greek/Roman system and what we know in English. Instead of the goddess of love, they opted for Odin’s wife Frigg (or Freda). The day was known as frigedæg and later simply fridai.
The Germanic tribes didn’t assign a god to this day of the week. Instead, they kept the Roman name of Saturni, shifting to sæterdæg and later saterday.
Every time you mark a date on your calendar, you’re actually honoring ancient gods and goddesses that go back thousands of years.