Interestingly the first mitzvah given by God in Egypt to the recently freed Jewish slaves was that to sanctify the new moon. That is, to sanctify a system of time that was lunar and not solar. Why was this the first mitzvah? Why is the Jewish calendar month based on the lunar cycle and not the then widespread use of the solar year?
The first possible reason that the sanctification of time was the first mitzvah given to the newly liberated Jewish slaves was that slaves don’t have time of their own. They are at their master’s beck and call 24/7 and God liberated the slaves and told them that now time is theirs but they must start off by sanctifying it. How much time do we waste during each day when we could be engaged in more productive even holy tasks? We are no longer slaves and that gives us the responsibility to use our time wisely.
The second possible reason is that articulated by Rabbi Samson Raphael Hirsch in his amazing biblical commentary: The NEW moon (play on the Hebrew words for month and new – chodesh and chadash which are spelled the same way in Hebrew) is an institution for the periodical fresh spiritual and moral rejuvenation of Israel by returning to God and his commandments. The new month and our new beginning each month proclaims salvation from sin and evil and that is why this institution stands at the commencement of the building of our nation and this is what differentiates us most sharply from all paganism.
The Pagan knows no newness in the world, or humanity, or in his gods. To him all todays evolved from yesterdays and tomorrow must with absolute certainty follow from today. Just as he denies the creation by God of the universe from nothingness so too he denies the ability of humankind to recreate their moral nature. According to the pagan guilt and evil must forever only beget guilt and evil. For us Jews the model is the new moon just as it bound by physical laws rejuvenates itself, so are you of your own free will able to create your own rejuvenation.