Judaism is doctrine, traditional practice, ethnicity and cultural norms. Linking all of them is national history. Most books of the Hebrew Bible focus on Jewish history. Purim, Passover, Shavuot, Tisha b'Av and Hanukkah commemorate events.
Tisha b'Av (the ninth of Av) falls this year on July 30, and marks the destruction of the First Temple in 586 BCE and the Second Temple in 70 CE.
Religious Jews fast, mourn and read the Book of Lamentations. Banks, public facilities and places of sport and entertainment close. Radio and television broadcast programs with historic themes and avoid commercials. Secular Jews go about their business as usual, but are likely to notice something different, if only that the gym or restaurant is closed.
This is a piece of being a people with a shared past, where history is a central ingredient in the tribal religion.