When yom tov falls out on Friday or Sunday, and an egg is laid on the first day of the two consecutive holy days, can you eat it on the following day? Of course, the answer is a machloket, and the essence of he dispute seems to be whether the holinesses of the two days make one long holiness, or whether they are two distinct holinesses. Which also boils down to a discussion of preparation for Shabbat to yom tov, and vice versa, under this discussion. Also, the second day of holiday in the Diaspora, and the way the calendar works to set up how yom tov comes to be when it is.