Shortly before sundown on the 29th of Adar, G-d commanded Moses regarding the mitzvah of sanctifying the crescent new moon and establishing a lunar calendar. This is the first mitzvah the Jews were given as a nation.
Moses had difficulty envisaging the moon's appearance at the exact moment of its monthly rebirth. After the sun set, G-d showed Moses the crescent new moon of the new month of Nissan, showing him the precise dimensions of the moon at the moment the new month is to be consecrated.
For the generations that followed, each new month was ushered in when two witnesses testified before the Sanhedrin (rabbinic supreme court) that they had seen the molad, the new moon. In the 4th century CE, Hillel II foresaw that the Jews would no longer be able to follow a Sanhedrin-based calendar. So Hillel and his rabbinical court established the perpetual calendar which is followed today -- until Moshiach will come and reestablish the Sanhedrin.
Links::
Lunar Time
Rosh Chodesh
The Molad
A few months after its creation, Napoleon's "Sanhedrin" (rabbinical supreme court) was dissolved. The Sanhedrin was created to approve certain religious regulations requested by the French "Assembly of Notables." The regulations were designed to blur the distinction between Jews and non-Jews.
The rulings of this pseudo-Sanhedrin were never adopted by Jewish communities.
Link:: Napoleon Bonoparte
When the Creator came to create the human being, Truth said, "Do not create him, for he is full of lies.
Kindness said, "Create him, for he will do acts of kindness."
What did the Creator do? He cast Truth earthward, and created the human being.
That is why it says, "Truth will sprout from the earth."
—Midrash Rabba
Every argument in Torah can be reduced to the same crucial question:
Do we follow rigid, immutable truth, regardless? Or do we take into account the particulars of this situation? Do we look only from above-down, or do we take the view from below as well?
The debate is never easy, because truth is no longer truth once compromised. Rather, we need to find a way to hold both ends of the stick at once.
That is why the debate must occur among us human beings here on earth, and from there the resolution must sprout. For only in that way will Truth come down to earth, where it truly belongs.