Christmas is the second of five cardinal feasts of the Catholic liturgical year.
Advent is the liturgical period that encompasses the four Sundays before Christmas. Since the nineteenth century in Northern Europe, most recently in other European countries, Christians prepare 4 candles. Every Sunday they light a candle, and then one more each following Sunday. These candles symbolize the light that will be reborn on Christmas Eve. These candles are often combined on the same support, the most common having a crown shape in which the candles are divided. This crown is called Advent wreath. In the countries of northern Europe and the USA, such a crown, with no candle, can be hung outside the houses, on the doors. It is usually made of small leafy branches held by colorful ribbons.
From this period was born the tradition of the Advent calendar: it consists of a large board precut cardboard, in which small windows open, one a day since December 1 until Christmas (24 days). Each window contains a phrase from the Gospel (Christian version), or a small candy or toy (secular view).
From a liturgical point of view, religious communities and some Catholic churches, during Vespers before Christmas, meet former O Antiphons and the hymn Veni, Veni, Emmanuel. Generally sung between 17 and 23 December, they symbolize a crescendo of waiting on the arrival of the Messiah. Some traditions, specific to these antiphons, are sometimes still alive.
Among Catholics, at midnight Mass, December 24 in the evening, is celebrating the Nativity of Jesus. Traditionally it began at midnight; today it takes place more often in the early evening. Catholic liturgical calendar provides a cycle of four Masses for Christmas, Christmas Masses. Midnight mass is the second.