Leilu Nishmat Reb Eliyahu Tzion ben Reb Chananya Niasoff ז"ל 
And in the merit of our partner in Torah Yigal Yisroel ben Sofia שיחיו 

Understanding the Jewish Calendar: The Math & the Psychology
The Two Phases of Jewish History in Responding to Crisis
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Class Summary:
This class, presented on Sunday Parshas Bo, 2 Shevat 5777, January 29, 5777, at Ohr Chaim, Monsey, NY, explores the structure of the Jewish calendar.

Given the inherent challenges of a lunar based calendar (including the fact that it needs to be synchronized with the solar seasons), why did the Torah choose set up the calendar and base Jewish life around the moon? Also, what is the significance of the fact that for the first half of Jewish history we established our Rosh Chodesh based on live witnesses who observed the moon; yet, for its second half, the system was altered to follow a pre-set calendar. And if the calendar is a fair way of navigating time, why did the Torah demand that the optimal way of establishing the first day of the month is through the tedious and complex process of witnesses traveling to the court and being cross examined there? Why not always use the calendar?

Third, why is the mitzvah of sanctifying the new moon told to Moses as a prelude to the redemption of the Jews from Egyptian bondage? What connection is there between the moon’s renewal and the Egyptian Exodus? And why right now? It is strange that with so much going on, G-d decides at this precise moment to discuss the Jewish calendar! The end is near; liberation is about to happen. Why are we now concerned with the calendar?

Fifth, why was this the first mitzvah given to the Jewish people, days before they were to become a free nation? 

In a deeply moving address in 1959, the Lubavitcher Rebbe offered a majestic and heart stirring explanation.