The first of Nissan and the first of Tishrei mark the beginnings of the Jewish year. The solar aspect of our calendar—representing the fixed laws of nature—begins in Tishrei; whereas the lunar cycle—symbolizing the ups and down of Jewish history—begins on the first of Nissan.
During Jewish leap years, Parshat HaChodesh, the special maftir portion we read on the Shabbat before Rosh Chodesh Nissan, generally coincides with Parshat Tazria. At first glance, these two parshiot seem to have little in common—Parshat Tazria being one of the most technical and driest parshiot in the Torah, dealing with the intricate and no longer applicable laws of tzara’at. Parshat haChodesh, on the other hand, describes the preparation for and excitement of the Exodus, the most powerful and relevant event in all of Jewish history.