The Three Weeks or Bein ha-Metzarim (Hebrew: בין המצרים, "Between the Straits") (cf "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 Shiva Asar B'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 siege of Jerusalem by Nebuchadnezzar II occurred in 586/7 BCE, and the second siege of Jerusalem (70) by the Romans, in 70 CE. Jewish chronology, however, traditionally places the first destruction at about 421 BCE. (See Missing years (Hebrew calendar) for more information.) Observances The mourning observances during the Three Weeks are divided into four levels, increasing in intensity: From the Seventeenth of Tammuz until the end of Tammuz From Rosh Chodesh Av until the week in which Tisha B'Av falls The week in which Tisha B'Av falls until the Eighth of Av Tisha B'Av itself Standard Ashkenazic custom, or minhag, restricts the extent to which one may take a haircut, shave or listen to music, though communities and individuals vary their levels of observance of these customs. No Jewish marriages or other major celebrations are allowed during the Three Weeks, since the joy of such an event would conflict with the expected mood of mourning during this time. Many Orthodox Jews refrain from eating meat during the Nine Days from the first of the month of Av until midday of the day after the fast of Ninth of Av, based on the tradition that the Temple burned until that time. Time of danger The Three Weeks are considered historically a time of misfortune, since many tragedies and calamities which befell the Jewish people are attributed to this period. These tragedies include: the breaking of the Tablets of the Law by Moses, when he saw the people worshipping the golden calf; the burning of a Sefer Torah by Apostomus during the Second Temple era; the destruction of both Temples on Tisha B'Av; the expulsion of the Jews from Spain shortly before Tisha B'Av 1492; and the outbreak of World War I shortly before Tisha