29th July, 2022: Rosh Chodesh Av - Time Of Teshuvah!
On the Biblical calendar, the fifth month of the year (counting from Nisan) is called "Av" (אָב) in Jewish tradition. The month of Av is traditionally regarded as the most tragic in the Jewish calendar. On the first day of this month, Aaron (the first High Priest of Israel) died (Num. 33:38), which was considered a ominous event. On the ninth day of the month (i.e., Tishah B'Av), the LORD decreed that the original generation rescued from Egypt would die out in the desert and be deprived from entering the Promised Land because they believed the faithless report of the Spies (Num. 13-14). Later both of the Holy Temples were destroyed on the ninth day of Av as well... 
Because both Temples were destroyed on the ninth of Av, this date is remembered as lowest point of the "Three Weeks of Sorrow" (שלושה שבועות של צער) that began with the fast of the 17th of Tammuz (undertaken to recall both the shattering of the tablets after Moses discovered the people worshiping the golden calf and also the breach in the walls of Jerusalem by the Babylonians before the First Temple was destroyed). During this three-week period, weddings and parties are forbidden: It is a time for solemn reflection and mourning for Israel...
The Three Weeks of Sorrow
As mentioned above, the Fast of Tammuz marks the beginning of the "Three Weeks of Sorrow," a 21 day period of national mourning which is completed on Tishah B'Av. The Mishnah further associates the fast of Tammuz as the "Fast of the Fourth Month," mentioned by the prophet Zechariah (Zech. 8:19). The purpose of this fast is to instill a sense of teshuvah (repentance) by recalling specific tragedies that befell the Jewish people because of idolatry.
The period between the fourth and fifth months is a somber time of reflection for many Orthodox Jews. The three weeks from Tammuz 17 to the Av 9 is called bein ha-Metzarim (בֵּין הַמְּצָרִים) - "between the straights" (based on Lamentations 1:3), a period of time during which many calamities befell the Jewish people. Since both Temples were destroyed during this period (i.e., between the 4th and 5th months), the sages established this extended period as a time of mourning for the Jewish people.
Typically marriages are not held during this period, and many Jews deliberately refrain from ostensibly pleasurable activities, such as listening to music, dancing, taking vacations, and sometimes even shaving! In fact, most Orthodox Jews will refrain from any activity that might require the recitation of the Shehecheyanu blessing.
In short, the Three Weeks of Sorrow is a time for reflection and mourning over the destruction of the Temple and therefore constitutes a time of corporate reflection intended to lead Israel to teshuvah (repentance).
Menachem Av
The period immediately following Tishah B'Av and continuing through the month of Elul is called the "seven weeks of comfort" (shiva d'nechemta: שְׁבְעָה דנחמתא). The Haftarah for each week during this period foretells of the glorious future of the Jewish People. Because of this, some Jews use the name "Av" through the Tishah B'Av and afterwards use the name "Menachem Av" (i.e., the Comforter of Av).