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
In the month of Elul, the month before Rosh Hashanah, a signal goes out to every Jewish soul that it is time to return to the palace that is home.
It is a signal both subtle and loud.
Subtle, because it does not awaken even those who are closest—every soul must awaken itself. Loud, because it reaches those who have been thrown to the edge of the universe.
Loud, because it is a signal of love and joy. Subtle, because it is an intimately personal call.
Loud, because it provides immeasurable powers to break out of whatever holds you back, lift you above all obstacles, and carry you all the way home. Subtle, because the power is there, but latent, quiet, awaiting your determination.
How can a signal be both subtle and loud, joyful and intimate, empowering and latent?
Because this signal originates from the very origin of your own soul, that place from which your soul was torn but has never truly abandoned. And as distant as a soul may stray, as lost as she may be, she will always remain one with her Beloved.
And now she hears her Beloved call, from a place deep within herself.