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
We all suffer a maddening delusion of being something separate from G‑d. The delusion of “I.”
We cannot heal it, because yes, we exist, for He created us.
We cannot live with it, because this chilling notion of otherness is a denial of the truth.
But we can resolve it in the act of learning Torah. In learning Torah, He speaks with us. If there were no other, with whom would He speak?
We can resolve it in prayer. In prayer, we speak with Him. If there were no other, who would speak with Him?
We can resolve it in every mitzvah. Through every mitzvah, we become one with Him. If there were no other, two would not become one.
Now the reality of our otherness is no longer simply a delusion, but a treasured artifact of a divine desire: that two should become one.
As Adam, the primal human, said, “This ‘I’ was created to serve its Creator.”