Jewish people observe tisha b’av each year to commemorate the destruction of the ancient temples in jerusalem and the subsequent persecution of jewish communities throughout history. Tisha b’av is a jewish fast day that occurs on the ninth day of the month of av, or if that day happens to be shabbat, then on the 10th day of av.
Therefore, one may not eat meat, drink wine, wash. Tisha b’av is the saddest day on the jewish calendar, tisha b’av primarily commemorates the babylonian destruction of the first temple in 586 bce and the roman destruction of the second temple by the romans in 70 ce.