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
The sages describe the Torah as the wisdom by which the world was made. But that does not capture its essence. It is far beyond that. Torah is the wisdom by which the world is healed.
To heal a world, you must stand entirely beyond it. You must enter into the very essence of its Creator and sense what He wanted from this world to begin with. In the story of creation, you will find whispers of an unfathomable Author. In its healing, you will discover the Author Himself.
That is why Torah was initially given to survivors, to people who had suffered lives marked by trauma, yanked out of the darkest pits of human existence at the last possible moment. To people who had to be told not to steal, not to murder, not to covet that which belongs to someone else.
Because it is when Torah reaches you at your lowest point and pulls you out of there that you see its very essence and deepest power.
And it is when you have been to the rock bottom of human experience and back that you have the power to grasp the Torah at its essential core. To sense the Author within the command.