Commemorating the Exodus
In Parshat Bo, as the Jews prepare for the Exodus from Egypt, God designates Nissan as the first month of the Jewish calendar. This is difficult to understand, given that we commonly refer to Rosh Hashana - the first day of Tishrei - as the new year, marking the Creation of humanity.
The explanation is as follows: Often people accept the idea of God as Creator. But they figure that after Creation, God sat back to let nature run its course. The Exodus, however with all its open miracles - teaches us that God's role as Director of History, is even greater than His role as Creator. And that's why at the Exodus, the order of the months changed - to commemorate this new relationship between God and humanity.
Actually, this helps explain another question: If Shabbat is a commemoration of the Six Days of Creation, then why are only Jews commanded to observe Shabbat?
The answer is found in the text of the Friday night Kiddush, where we declare that the purpose of Shabbat is "to remember Creation and to remember the Exodus." Because while God created the entire world, it was through the Jewish Exodus from Egypt that mankind came to appreciate God as the guiding hand of history.
Let's listen to the words of Prof. Nicholai Berdysev, writing in Moscow in 1935: "The survival of the Jews, their endurance under absolutely peculiar conditions, and the fateful role played by them in history - this people is governed by a [mystical] predetermination, transcending the norms of history."