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
And these words with which I connect with you today… (Deut. 6:6)
Every day these words should be just as new for you as if they were given today. (Sifri)
How could the same mitzvah you did yesterday be new to you today? The same words of Torah as though you never knew them before? The same prayer as though you never said it before?
Through a simple meditation on what is happening when you do that mitzvah, when you study those words, when you pour out your heart in your prayer.
Contemplate that the entire universe is but a glimmer of G‑d’s infinite light. Yet, in this mitzvah, you hold the Creator Himself in your hands. As you learn His Torah, your soul joins with His very essence. In your prayer, you and He are alone as one.
It makes no difference that you feel nothing, that you are not awake to the glory of this moment, that the physical body does not allow you to perceive reality as it is. One day you will see this moment now from a place far beyond this coarse world.
But then it will be only a memory, a souvenir.
Now you have the real thing.
Because, says G‑d, today, in the moment of this mitzvah now, I, just I, beyond any name or definition, I connect with you.
And such a moment is a moment beyond time.