When Is Tu B'Av. Tu b’av means the 15th day of the month of av in the hebrew lunar calendar. Tu b’av is an auspicious holiday celebrated in judaism, thought of in more modern times as the “festival of love.”.
Tu b’av, or the 15th of av, is considered a minor jewish holiday and is known as the day of love or kabbalistic valentine’s day. A month and a half before rosh hashana.