Universal law provides that the days of penance in the Latin rite are every Friday of the year and the whole season of Lent (canon 1250). But universal law isn't the only kind of law. There is also particular law, or law that applies to particular territories or groups of people within the Latin rite.
Such as the diocese of the United States.
It may come as a surprise to some, but today--Monday, January 22--is a day of penance according to the particular law of the Latin rite in the United States.
According to the General Instruction of the Roman Missal:
In all the dioceses of the United States of America, January 22 (or January 23, when January 22 falls on a Sunday) shall be observed as a particular day of penance for violations to the dignity of the human person committed through acts of abortion, and of prayer for the full restoration of the legal guarantee of the right to life. The Mass "For Peace and Justice" (no. 21 of the "Masses for Various Needs") should be celebrated with violet vestments as an appropriate liturgical observance for this day (GIRM 373).
The law does not require fasting or abstinence today, though a person may do these if he chooses. Strictly speaking, the law does not require that individual Catholics perform penance as a matter of obligation on this day, but it's certainly in keeping with the spirit of the day to do it voluntarily.
For those from other nations--or those who are simply wondering why January 22 was picked--the answer is that it's the anniversary of
THE EVIL DECISION.
Please pray for an end to abortion.
ONE BISHOP SPEAKS.
(CHT to the reader who e-mailed.)