It is clear that any child without prejudice would understand that the same tragedy cannot always occur on the same day of the year after always announcing it on another specific day.
The 9 Av is considered the saddest day of the Jewish calendar and is therefore believed to be a day destined for tragedy
Jewish calamities occurred on 9 Av
1-The first temple built by King Solomon was destroyed by Nebuchadnezzar
2-The Second Temple built by Ezra and Nehemiah was destroyed by the Romans
3-The Romans crushed the Bar Kokhba revolt and destroyed the city of Betar, killing more than 500,000 Jewish civilians
4-The First Crusade caused 10,000 Jews to be killed in their first month and destroyed Jewish communities in France and Renaia
5-The Jews were expelled from England
6-The Jews were expelled from France
7-The Jews were expelled from Spain
8-Germany entered World War I, which caused massive turmoil in European Jews and whose aftermath led to the Holocaust
9-SS commander Heinrich Himmler formally received the approval of the Nazi Party for "The final solution." As a result, the Holocaust began during which almost a third of the world's Jewish population perished.
10-Mass deportation of Jews from the Warsaw Ghetto began on the way to Treblinka
11-The bombing of AMIA, in the center of the Jewish community in Buenos Aires, killed 85 people and wounded 300
12-The Israeli withdrawal from Gaza began in the Gaza Strip, expelling 8,000 Jews living in Gush Katif