This sugya discusses the obligation of reading the megillah on Purim day, and also the night before. Specifically, it discusses the source of the nighttime megillah obligation - whether it is part of the original takana of the Neviim (to read the megilla by day), or if it is a new takana from Chazal. We will discuss the reason why the nighttime reading was added. We also study how this affects other aspects of Purim, such as the Bracha of Shehecheyanu during the day, and how this may also affect the Halachos of Mishteh and Simcha by night.