Adar 9

Adar 9 is the traditional date of the first controversy between the talmudic academies of Hillel and Shammai. In the first century CE, Roman persecution of the Jews led to a weakening of Torah education channels, and two separate rabbinic schools came into being, each developing its own set of customs. However, the Hillel and Shammai academies worked together in a spirit of mutual cooperation that prevented any schism from forming in the Jewish world.