Today’s Daf Yomi page, Eruvin 39, is all about yom tov sheni, or the second day of the holiday we celebrate everywhere outside of Israel. But why do we celebrate it? And is it time, now that we have powerful apps that can tell us precisely when holidays begin and end, to put an end to this custom? Or were the wise rabbis trying to teach us something more valuable, a lesson about holding on to tradition with all of our might? Listen and find out.