Origin of seven days in the week

The origin of seven days per week appears to be astronomically related back to the Babylonians.

According to this ancient astronomy it is because there are 7 astronomical objects in the sky that can be observed. This includes:

  • the sun
  • the moon
  • 5 planets (Jupiter, Venus, Saturn, Mercury and Mars)

It is also thought that 7 days is a simplification of a quarter of a lunar month.


A typical calendar week, starting on either Sunday or Monday.