In February 2002, the Catholic Church established that throughout the United States,Read more at Aquinas and More where they have a good explanation and also some ideas if you are not sure what you want to do.
January 22nd would be observed as a day of prayer and penance against abortion:
“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. 22 of the 'Masses for Various Needs') should be celebrated with violet vestments as an appropriate liturgical observance for this day.”
– General Instruction of the Roman Missal, no. 373
I'm posting this a day early so it won't be a complete surprise.