Five tragedies are said to have occurred on the 17th of Tammuz: the breaking of the tablets of the Ten Commandments by Moses, the cessation of the daily offering during the Babylonian siege of Jerusalem, the burning of the Torah by Apostomos, the placing of an idol the Temple in Jerusalem and the breaching of the walls of Jerusalem by the Romans in 69 CE after a long siege. According to the Jerusalem Talmud, the Babylonians also breached the walls of Jerusalem on this day.
During the three weeks, many Jews begin following mourning customs, including avoiding haircuts and shaving, not listening to music and not getting married. Many also avoid risky or dangerous activities and traveling.
Additional restrictions are practiced starting from the first day of the Hebrew month of Av until the ninth day of the month, the fast of Tisha B'Av, commemorating the destruction of the Temple in Jerusalem, among other calamities. Eating meat and drinking wine and wearing freshly laundered or new clothes is prohibited. Joyous activities, such as bathing for pleasure and buying new items, are avoided or prohibited. One should consult their rabbi for any questions about Jewish laws and customs during this time.
The fast of the 17th of Tammuz, also known as Shivah Asar B’Tammuz, begins at dawn and ends at nightfall. One may wake up before the fast and eat, as long as one had mind to do so before going to sleep. Those who are ill, pregnant or nursing may not need to fast and should consult a rabbi.
Last year, Israel's Chief Rabbi David Lau ruled that those who test positive for the coronavirus or feel symptoms of the virus should not fast.
Fast Start and End Times: (According to MyZmanim. There are varying customs)
Jerusalem
Start: 4:08 AM
End: 8:20 PM
Tel Aviv
Start: 4:08 AM
End: 8:22 PM
Haifa
Start: 4:04 AM
End: 8:24 PM
Eilat
Start: 4:18 AM
End: 8:14 PM
Beersheba
Start: 4:12 AM
End: 8:20 PM
New York
Start: 3:38 AM
End: 9:22 PM (According to Rabbi Moshe Feinstein, those who have trouble fasting may eat at 9:13 PM)
Los Angeles
Start: 4:12 AM
End: 8:53 PM (According to Rabbi Moshe Feinstein, those who have trouble fasting may eat at 8:45 PM)