The Jewish calendar marks three pilgrimage festivals and twelve new moons. The Kitzur ShLaH explains that the three festivals correspond to the three patriarchs: Abraham, Isaac, and Jacob. The twelve new moons correspond to the twelve tribes.
But the twelve new moons are given, in a special sense, to the women of Israel. Why? Because when the tribes sinned with the golden calf at the foot of Sinai, the men came first, tearing off their gold rings to throw into Aaron's crucible. The women refused. They would not hand over their earrings for an idol, no matter how loudly their husbands insisted.
The tribes, having sinned, needed atonement. The Kabbalistic tradition of Rav Isaiah Horowitz teaches that the last day of each month is called the "little Yom Kippur," and pious souls fast and do teshuvah on it. The first day of the new month, by contrast, is a minor festival when the custom is to prepare an extra dish in honor of the day, particularly for the women of the household.
So the twelve months became a monthly reward for the women who stood firm at Sinai. While their husbands had to keep asking forgiveness at each month's close, the women were handed the first of each month as a quiet celebration of the courage that once refused a calf.
The lesson is pointed. When idolatry marched into the camp, it was the women who held the line, and Heaven still keeps their receipt on the calendar.