If you’ve ever tried to get a rabbi to marry you during the summer, you’ve probably heard of Tisha B’Av–a fast day that commemorates the destruction of the First and Second Temples. (This year it starts the night of July 28th.)
The Three Weeks kicks off this Sunday–the 17th of Tammuz. It’s believed that a lot of bad stuff happened to the Jews on this day. Moses broke the original Ten Commandments after coming upon the Israelites as they worshiped the Golden Calf. The Roman rulers forbade sacrifices to be made in the Second Temple on this date in 69 C.E.. In the following year, the walls of the Old City of Jerusalem were breached. This attack led to the destruction of the Temple three weeks later.
So, in commemoration of all that, it is traditional to fast from sunrise to sunset.
We will not say “Happy 17th of Tammuz” because that sounds wrong.