Be sure to make it Mass on January 1. It's a Holy Day of Obligation for the Universal Church. Don't just drag yourself to Mass because you are "obliged" to, go with joyful anticipation to celebrate this great feast with the angels and the saints. The traditional calendar celebrates the Octave Day of the Nativity, and the new calendar, the Solemnity of the Blessed Virgin Mary. Even though there are different feasts being celebrated in the new and traditional calendars, any valid Catholic Mass will fulfill your obligation to attend Mass this day. Just remember to treat the remainder of the day as you would a Sunday; it is a holy day.