Regarding the chagim (festivals), we know that a chag is really one day (not including the rabbinic chag a/k/a yom tov sheini). However, for Rosh hashana, Israelis observe a two day festival. So is ...
The Biur Halacha in Siman 299 brings an interesting opinion from the Magen Avraham. If someone was fasting (and had taken on to fast for a few days) and wasn't able to make havdallah Motzei Shabbos ...
Why does the Shaliach Tzibbur start Shacharis on Shabbos from Shochein Ad, on Yom Tov from HaKeil, and on Rosh HaShana/Yom Kippur from HaMelech?