I know that a day represent the time for the earth to make a full rotation around its own axis and a year is the time for the earth to make a full rotation around the sun.

But does a week represent something? And a month?

Thank you.

ps: Not sure what tags I need to use, feel free to add/remove them

  • $\begingroup$ I've made some research but i haven't found this post. Thanks $\endgroup$ – TroyAndAbed Jun 30 '15 at 2:57
  • $\begingroup$ The duplicate post has some better information in its answer related to the significance of the quarters (they line up roughly with the phases of the lunar cycle). $\endgroup$ – called2voyage Jun 30 '15 at 13:19

The concept of a month derived from the amount of time it takes for the moon to cycle from new moon to new moon (which is roughly 29.5 days). The modern month has experienced changes from this original concept due to trying to fit a standard number of months within a solar year.

If you divide the lunar month into quarters, each quarter is approximately 7 days long. This is believed to be the origin of the seven-day week.


I'm pretty sure that weeks are seven days long because in ancient times people worshipped the sun, moon and the five then-known planets. The days are even named after these in various languages...

  • $\begingroup$ Andy, the Wikipedia article Keith Thompson linked says there is no evidence that the connection between the seven days of the week and the seven classical planets goes back to the original Babylonian establishment of the seven-day week. $\endgroup$ – called2voyage Jun 30 '15 at 13:17
  • $\begingroup$ You're right, my understanding of it has always been that originally they used weeks of seven days, plus a longer week to make up the missing day or two. I was trying to pin down the significance (if names are "significant") of the slightly more modern week though. Hope that's OK :) $\endgroup$ – Andy Jun 30 '15 at 13:59
  • $\begingroup$ Sure, I suppose it is on topic since it relates to the planets. $\endgroup$ – called2voyage Jun 30 '15 at 14:00

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