The Jewish month follows the moon's cycle of 29 days and a half. That is why sometimes we have one day of Rosh Chodesh and sometimes (roughly: every other month) two days.
In those 29 days and a half the moon grows from virtually nothing until its plenitude, and then decreases and disappears, to be visible again. Our Rabbis talked about the resemblance between the cycle of the moon and the permanent renewal of the Jewish people.
"Whereas the sun is the symbol of unchanging nature, rising in the east, setting in the west, day in and day out every day of the year, the moon changes and it seems to be telling us something: You can be small and you can diminish until you almost disappear, but then, when things look their darkest, hope springs eternal. You can start looking up again. You can change a situation and yourself for the better, no matter how bad it seems. Nothing is static or set in stone. Human beings have free will and therein is their power of renewal -- an ever-present struggle against the steady, cyclical, repetitive and predictable march of time and nature."
The solar system determines the year, in Hebrew "shana," which comes from the same root as to repeat, to go over, whereas the moon sets the months, "Chodesh", from the Hebrew root "chadash," -- new, change, different.
The Jewish people are compared to the moon. Though they are small, and suffering has been an integral part of our history among the nations, we Jews know never to give up. As an individual and as a nation, we will rise up again and light up the night.
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