In the Bible God has named the fifth month of HIS Biblical Calendar as simply, FIFTH MONTH. The name “AV” used for the fifth month on the Jewish calendar was adopted after the Babylonian exile, likely around the 5th century BCE. However, before the exile, the months were referred to by number (e.g., “Fifth Month”). The Hebrew month of Av, which is from mid-July until mid-August (USA) gets its name from the Babylonian calendar. In Babylonian, the word “Av” likely meant “father”. While the name itself is of Babylonian origin, it’s interesting to note that in Hebrew, the word “Av” (אָב) primarily means “father” and this connection is often highlighted during the month, especially in the context of Tisha B’Av, the day of mourning for the destruction of the Temples in Jerusalem. Some traditions also add “Menachem,” meaning “comforter,” to the name, referring to God as the comforter of the Jewish people.

The Fifth Month on God’s Biblical Calendar is still listed today as Av on the Jewish Religious Calendar, and it is still positioned as the fifth month of the year beginning with Nisan as the beginning of the year.  Exactly who assigned this name to the  month on the Jewish calendar is not clear.  It is a summer month of 30 days that occurs on the Gregorian calendar we use in the USA from mid-July thru  mid-August.

While the name “Av” itself does not appear in the Bible, the month is significant in Jewish history and tradition. In the Bible GOD refers to each month by its numerical order in the calendar year, and Av is recognized as the Fifth Month.  One of the most significant events associated with the Fifth Month (Av ) is the destruction of the First and Second Temples in Jerusalem, both of which are traditionally believed to have occurred on the ninth day of Av, known as Tisha B’Av. This day is observed as a day of mourning and fasting, commemorating the calamities that have befallen the Jewish people throughout history.

Here are just some of the Biblical events that occured in the Fifth Month. 

1 Av (circa 1273 BCE) – Aaron, the first High Priest, brother of Moses and Miriam, passed away at age 123 on the 1st of Av of the Jewish year 2487 (1274 BCE).
1 Av (513 BCE) – Ezra and his followers arrive in Israel
7 Av (586 BCE) – First Temple invaded by King Nebuchadnezzar[5]
7 Av (67 CE) – Civil war breaks out in besieged Jerusalem; one group set fire to the city’s food stores, which is said to have quickened starvation.
7 Av (1492 CE) – Jews of Spain expelled by King Ferdinand and Queen Isabella.
9 Av (1312 BCE) The Twelve Scouts sent by Moses to observe the land of Canaan returned from their mission ater 40 days. Only two of the scouts, Joshua and Caleb, brought a positive report, while the others spoke disparagingly about the land. The majority report caused the Children of Israel to cry, panic and refuse to enter the “Promised Land”. For this, they were punished by God that their generation would not enter the land.
586 (BCE) The First Temple is destroyed by the Babylonians and Nebuchadnezzar.
70 (BCE) the Second Temple is destroyed by the Romans.
135 (CE) The Bar Kochba revolt, a rebellion of the Jews of the Roman province of Judea, led by Simon bar Kochba, against the Roman Empire was crushed by the Roman Emperor Hadrian.
136 (CE) the Temple Mount was plowed under, and Jerusalem was rebuilt as a pagan city.
1096 (CE) the First Crusade is officially commenced, killing 10,000 Jews in its first month and destroying Jewish communities in France and Rhineland.
1290(CE)  The Jews are expelled from England.
1492 (CE)  The Jews were expelled from Spain.
1914 (CE) World War I begins when Germany declares war on Russia – launches persecutions against the Jews in Eastern Russia. (August 1, 1914)
1941 (CE) Henrich Himmler commander of Hitler’s Schutzstaffel, and later of the Gestapo in Nazi Germany received approval for “The Final Solution” which resulted in the Holocaust in which nearly one third of the world’s Jewish population perished.
1942 (CE) The mass deportation of Jews from the Warsaw Ghetto was the largest of all the Jewish ghettos in German-occupied Europe during World War II.
1994 (CE)  The bombing of the Jewish Community Center in Buenos Aires in Argentina, killing 85 and injuring 300.
2005 (CE) The Israeli disengagement from Gaza, expelling 8,000 Jews from Gush Katif, which was a block of 17 Israeli settlements in the southern Gaza Strip.

Sources: Wikipedia / https://en.wikipedia.org/wiki/Av and The Sacred Calendar.com / https://www.thesacredcalendar.com/book-of-joshua-conquest-of-canaan