WordNet (r) 3.0 (2006):

January 1
    n 1: (Roman Catholic Church and Anglican Church) feast day
         celebrating the circumcision of Jesus; celebrated on
         January 1st [syn: Circumcision, Feast of the
         Circumcision, January 1]
    2: (Roman Catholic Church) a holy day of obligation [syn:
       Solemnity of Mary, January 1]
    3: the first day of the year [syn: New Year's Day, New
       Year's, January 1]