A Week for Each Moon Phase
The reason why we organize our lives around a 7-day week is, quite literally, above our heads. Like many other calendars, today's Gregorian calendar is ultimately based on the phases of the Moon. It takes the Moon just over 29 days to cycle through all Moon phases.
Moon phases in your city
For everyday purposes, this is a fairly long and impractical time span, so it makes sense to break it down into smaller segments.
Enter the Babylonians. This ancient society, who lived in Mesopotamia in what is now Iraq, rounded the Moon cycle down to 28 days and divided this time span into 4 periods of 7 days each, using leap days to stay in sync with the Moon phases in the long-run.
