A day is when earth completes a rotation – so makes sense we have the concept of days. It’s an actual event.
A year is when earth completes one revolution around the sun – so makes sense we have the concept of year.
But why did we invent the concept of months or weeks? What purpose do they service?
Why couldn’t we just count day 1 to day 365 as dates.
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i think the calendar was probably invented by women because you need to keep track of 28-30 days in order to track menstruation. also the moon completes one revolution around the earth every 28 days so maybe visually that was also used to track the time/months. not sure what came first though.
A month is the period the moon takes to orbit around earth and is the basis of the lunar calendars, and is something you could see with your naked eye.
A week just makes things easier to organise I guess
Others have explained the month, which comes from the cycles of the moon (the words “month” and “moon” are etymologically related).
The week has no astronomical basis. While it was used in the bible and by the Romans, there’s evidence that the ancient Sumerians and Babylonians used it first. They divided the year into periods of 7 days, including one day dedicated to recreation.
https://www.britannica.com/science/week
Practically speaking, a year or a month is a very long time to plan things and establish a routine. 7 days is a more reasonable schedule and more practical to use for day-to-day business, if we’re talking things like, “We go to market on Tuesday, we clean the drapes on Wednesdays…”
As far as why it’s 7 and not 8 or 5, that’s probably because early peoples named the days after the astrological bodies they could see – five planets, sun, and moon.
The French Revolution led to the creation of the metric system (still in use) and the republican calendar (discontinued after Napoleon took over). In the republican calendar, there are years and months, each month 30 days long, and comprised on 10 day weeks. Extra days were added to make it 365 or 366 in leap years. As noted already, years and months are owning to the yearly and monthly lunar cycle. Name of the months corresponded to the seasons, so Thermador was a summer month, beginning in late July. Weekdays had numbers, not names.
Month also comes from the cycle of women where bleeding occurs every 28-30 days . So women HAD to keep track of the month and thus month makes sense .