The Seventeenth of Tammuz (Hebrew: שבעה עשר בתמוז, Shiv’ah Asar b’Tammuz) is the seventeenth day on the Hebrew month of Tammuz. This day is a half-day fast (dawn to dusk) in Judaism. This year the Seventeen of Tammuz is on July 19.

Background:

The 17th of Tammuz is mentioned in Nevi’im (Prophets) – as “the fast of the fourth month” (Zechariah 8:19). The Mishnah (Taanit 4:8) lists five calamities that befell the Jewish people on this date:

1. Moses broke the two tablets of stone on Mount Sinai;
2. The daily tamid offering ceased to be brought;
3. The walls of Jerusalem were breached (proceeding to the destruction of the Temple);
4. Prior to Bar Kokhba’s revolt, Roman military leader Apostomus burned a Torah scroll;
5. An idol was erected in the Temple.

The Babylonian Talmud (Taanit 28b) places the second and fifth tragedies in the First Temple, while dating the third tragedy (breach of Jerusalem) to the Second Temple period. Jerusalem of the First Temple, on the other hand, was breached on the 9th of Tammuz (cf. Jeremiah 52.6-7).

The Three Weeks or Bein ha-Metzarim (Hebrew: בין המצרים, “Between the Straits” or “In Dire Straits”) is a period of mourning commemorating the destruction of the first and second Jewish Temples. The Three Weeks start on the seventeenth day of the Jewish month of Tammuz – the fast of the Seventeenth of Tammuz – and end on the ninth day of the Jewish month of Av – the fast of Tisha B’Av, which occurs exactly three weeks later. Both of these fasts commemorate events surrounding the destruction of the Jewish Temples and the subsequent exile of the Jews from the land of Israel. According to conventional chronology, the destruction of the first Temple, by Nebuchadnezzar II, occurred in 586 BCE, and the second, by the Romans, in 70 CE. Jewish chronology, however, traditionally places the first destruction at about 421 BCE.

Observances:

Jewish law forbids during this time:

taking a haircut
shaving
listening to music
no Jewish marriages are allowed during the Three Weeks, since the joy of such an event would conflict with the expected mood of mourning during this time.