Shemini Atzeret is a Jewish holiday. It is celebrated on the 22nd day of the Hebrew month of Tishrei in the Land of Israel, and on the 22nd and 23rd outside the Land, usually coinciding with late September or early October. It directly follows the Jewish festival of Sukkot which is celebrated for seven days, and thus Shemini Atzeret is literally the eighth day. It is a separate—yet connected—holy day devoted to the spiritual aspects of the festival of Sukkot. Part of its duality as a holy day is that it is simultaneously considered to be both connected to Sukkot and also a separate festival in its own right. Outside the Land of Israel, this is further complicated by the additional day added to all Biblical holidays except Yom Kippur. The first day of Shemini Atzeret therefore coincides with the eighth day of Sukkot outside the Land of Israel, leading to sometimes involved analysis as to which practices of each holiday are to apply. Source: Duckduckgo API