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
Our world is a world where a rainbow could be.
At first, there was a world that only received and returned no dividends. Its inhabitants took no ownership. They lived with their Creator’s benevolence, they did what they did with no need for excuses, and eventually died as they died. And that was it.
With the Flood, this world was recreated. The earth was cleansed, the atmosphere purified. It became a world that could take the sunshine that poured in from above and refract it into many colors.
It became a world where a created being could be born, take the soul, body, share of the world and all the sustenance its Maker gave to it, use that, do something with that—and then return it, saying, “See what I have done with that which You gave me!”
And so, G‑d vowed to never destroy the world again. For, if the inhabitants would go wrong, they might always turn around and clean up their own mess.