i submit to you by observation a month is ~28 days
and there are four phases to the moon.
b'shem Y'shua
No, there are multiple phases of the moon. We can reduce it to four, in the same sense that a clock sometimes only has 12, 3, 6 and 9 on it. But the 7 days don't follow the phases of the moon well, or the full moon would always fall on a Friday, month after month, year after year. Also, there's nothing particularly special about 4. Sure, one can divide 28 by 4. But one can divide it by two as well, and get a 14 day week...that still doesn't really follow the moon cycle very well.
Conversely, depending on where you begin to measure a day, sometimes a month is 29 days, which is prime.