Re: week - year
Flatulent is right all is tied to the Moon.
You see, words "moon" and "month" are relative in English. In slovenian languages "moon" and "month" are the same word spelled like "mesiats" - (it means not full moon).
Every moon cycle has near 29 days 12 hours 44 seconds, so people can not make equal lenth in days for every months. But even if you would take 12 of such months - there will be phase shifting relativly to the 1/12 of Sun year, so you need to use more than 30 days in few months per year.
Week was setted for 7 days as it is 1/4 of moon cycle: babylonian priests have found four states of moon: full, left half (decreasing), new moon, right half (growing). There was a rule to sow the grain only in growing moon, and to cut hair in decreasing, not to lend money in decreasing moon. That superstition is living for our days too.