When to read the Megila? Megila 6b

The holiday of Purim occurs in the Jewish month of Adar. The Jewish calendar is lunar. To help keep it in sync with the solar year, the Rabbis regularly add a 'leap month' to the Jewish year, which means we can have a year with two months of Adar. The rabbis argue over in this situation whether to observe the holiday in the first or second Adar of a leap year. Rabbi Elazar the son of Rabbi Yose thinks we should read it in the first Adar, and that way not skip over a chance to do a mitzvah as soon as possible. Rabban Shimon ben Gamliel prefers the second Adar because it is followed immediately by the month of Nissan, where Passover occurs and we celebrate the liberation from Egypt. He puts it succintly - we should 'juxtapose redemption with redemption.'