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
There are two sorts of inner convictions of the soul, this thing we call faith.
Unbound by the confines of space and time, your soul sees a reality your mind cannot fathom. From that vision seeps down a conviction that G-d is with you, that He is good, and that there is really nothing else but Him.
Not because you understand. But because your soul sees that this is so. And she sees with a clarity and certainty the flesh eye could never attain.
Nevertheless, a higher vision means there are two and not one: There is you and there is the vision you perceive. And if there are two, two can be separated.
So that, when darkness and confusion swells and storms, threatening to rip you away from your G-d, a higher vision is not enough.
That is when you need to reach to the very core of your soul. Not to that place in the soul that sees G-d, but to the essence of the soul that is truly a part of G-d.
To say, "This is my G‑d. I am His, He is mine, and we are one."
"And so, nothing can stand between us."