Rosh HaShanah 21a and Rosh HaShanah 21b, getting the word of when RH or Pesah are to the faraway places, keeping two days of Pesah because we will have to keep two days of Sukkot, times for keeping two days of Yom Kippur, and then the idea of violating Shabbat for witnesses to get to Yerushalayim to declare the new month.
