8th Day is an American Hasidic pop rock band based in Los Alamitos, California. Formed in 2004 by brothers Shmuel and Bentzion Marcus, the group gained popularity in the Jewish music scene with their album Chasing Prophecy and its lead single, "Ya'alili", whose video became a minor viral hit on TH-cam. As of 2021, the group has released nine studio albums and one live album. They have performed at venues throughout the country and abroad including Lincoln Center for the Performing Arts, American Airlines Arena, and Universal CityWalk.