In the Roman Catholic Church , the second most important holiday is the Feast of the Nativity or the First Christmas , hich according to the Gregorian calendar is celebrated on December 25 . Christmas is one of the few holidays that have always been preceded by a vigil, ^11] popularly called Christmas Day ( December 24 ). The celebration of the birth of Jesus Christ thus extends over a slightly longer period of time. While Protestants focus their celebration on the early evening services on Christmas Day and on the morning services on December 25th, Roman Catholics focus their celebration mainly around midnight between December 24th and 25th. MasMass isis celebrated in this way directly at midnight and is therefore called midnight mass . n the Roman Missal , this Mass is called “In the holy night” ( In nocte ) an,d according to no prescription it does not have to be celebrated directly at midnight, but until 1960 the rubrics prescribed that “the first [Mass for the celebration of the Nativity] should be celebrated after midnight, after the end of the hymn Te Deum laudamus at Matins “. ^[12]