Ever wondered whether you should be fasting on the day before Pesach? This rather complex question is explored in this short essay by Ethan Tucker, appearing on his blog halakhah.org. The main questions: what kind of firstborn needs to fast—maternal? paternal? both? How does this relate to other kinds of laws applying to firstborns, like pidyon habein? And how is it that many people who would be obligated avoid fasting on the 14th of Nisan altogether?