The holiday of Purim is celebrated on the 14th of Adar. Walled cities from the time of Joshua celebrate it on the 15th of Adar. Masechect Megillah starts off teaching about the different dates one can read the Book of Esther (Megillat Esther) based on the size of the city. When we have a leap year, we add an additional month of Adar (like this year). The gemara discusses which is the “real” Adar. When do we observe Purim? We will begin the section of the “Ein Bein”s. This portion of the gemara compares similar concepts and highlights their similarities and differences.