Yom tov sheni shel galuyot

Yom tov sheni shel galuyot (Hebrew: יוֹם טוֹב שֵׁנִי שֶׁל גָּלוּיוֹת), frequently abbreviated as yom tov sheni (יוֹם טוֹב שֵׁנִי, 'second festival day'), means "the second festival day in the Diaspora". It is a principle in Halakha that mandates the observance of an additional day for Jewish holidays outside the Land of Israel.