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 is an outer world and there is an inner world. As deep as you penetrate, as high as you reach, there is always something breathing inside.
The outer world is made of things. Breathing inside the things are words.
Words are the outside. Inside the words are stories.
The story is the outside. Inside the story is a thought.
Thoughts are the outside. Inside the thoughts is a great light.
At the origin of all light is the beginning that cannot be known.
The outside we can touch and come to know.
The inside—we must wait and be still, so that it may speak to us.
As it did at Sinai. As it does whenever we learn Torah with all our heart and soul.