Tuesday, the 17th of Tammuz, is a fast day from sunrise to nightfall.
It commemorates the breaching of the walls of Jerusalem and inaugurates the
Three Weeks period of semi-mourning for the two destroyed Holy Temples in Jerusalem.
Articles #2-3 discuss the spiritual causes of the destruction.

Sunday (today) is the yahrzeit of the holy Ohr HaChayim, the great Kabbalist and sage from Morocco in the mid-1700's (see article 5 from his commentary on the weekly reading).