Exodus 12:2 "This month shall be to you the beginning of months"

Have you noticed how the moon changes its shape throughout the month?

At times, it shines brightly like a cream-colored ball.

Other times, we can compare it to a slice of honeydew. On some nights, it looks like a split banana! Sometimes, you can't see it at all!

While in bed watching the moon, take a peek through your window, shut your eyes for a moment and imagine a scene taking place many years ago in Eretz Yisrael.

In the Great Beit-Din, the chief Rabbi sits in his honored place, greeting the Jew who just arrived in the court.

"I saw the moon last night, Rabbi, and I believe it is the beginning of a new month," reports the Jew.

The Rabbi motions to a chart with many different moon shapes hanging on the wall. "Is this the shape you saw?" asks the Rabbi, pointing to a particular shape.

The man who witnessed the moon would be questioned until the judges were satisfied. When the judges heard proper testimony from at least two witnesses, they would declare that a new month had arrived.

Determining the new month is very important to the Jewish calendar.

HaShem commands us to celebrate specific holidays in their set seasons and on particular dates. In order to fulfill these commandments, we must know when a new month begins and count the days accordingly.

This way, we will be assured of celebrating the holiday on the correct date.

The Great Beit-Din (Sanhedrin) in Eretz Yisrael is commanded to determine and calculate the counting of the months.

The Rabbis knew when the moon would first begin to shine again. They informed the people to be alert and immediately report their findings.

Proper eye-witness testimony would serve as proof of the new month's arrival. Afterwards, news of the new moon would be spread promptly enabling all Jews to count the days of the month in a unified manner.

In this way, the Jewish calendar was set and followed.

In addition, HaShem commanded that the holidays of Pesach and Sukkot be celebrated in the spring and fall.

The Jewish calendar is a "Lunar Calendar" which means that it follows the phases of the moon. However, the seasons change according to the sun's yearly cycle.

There is an eleven and a quarter day difference between the cycle of the sun and the twelve lunar months.

Because of this, we might reach the proper Hebrew date for Passover, but the spring season will not yet have arrived!

There is a way to overcome this problem.

If such a situation arises, the Rabbis would foresee it and the Beit- Din would declare a leap-year.

The last month of the Hebrew calendar - Adar, would be doubled, (First-Adar and Second-Adar) and Pesach would then arrive in the spring time!

The Torah commands the Beit-Din to calculate the months and declare the necessary leap years. The manner in which it was done, as described above, applies only to the time of the Great Beit-Din in Eretz Yisrael.

Today, we follow the Jewish calendar which was established by Rabbi Hillel HaNasi, a descendant of Rabbi Yehuda HaNasi.

He calculated the precise arrivals of the new moon and the years which would be considered leap years.

We rely on this calendar until the arrival of Mashiach, when we will return to the original method of the eye-witness report.