I was able to find and English translation of the rubrics of the Mass, published in 1960. According to these rubrics, there are six seasons of the year, some of which of further subdivided, as follows:
1. The Season of Advent, which rune from First Vespers of the First Sunday of Advent to None of Christmas Eve.
2. The Season of Christmas, which is divided into Christmastide (
tempus Nativitatis) and Epiphany (
tempus Epiphaniae). Christmastide runs from First Vespers of Christmas Day to None on January 5. Epiphany runs from First Vespers of Epiphany to January 13.
3. The Season of Septuagesima, which runs from the First Vespers of Septuagesima to Compline of the Tuesday before Ash Wednesday.
4. The Season of Lent, which is divided into Lent (
tempus Quadragesimae) and Passtiontide (
tempus Passionis). Lent runs from Matins of Ash Wednesday to None of the Saturday before Passion Sunday. Passiontide runs from First Vespers of Passion Sunday to the Mass of Easter Vigil. Passiontide itself is further divided, in that from the First Vespers of Palm Sunday to the Mass of Easter Vigil is referred to as Holy Week, and the last three days of Holy Week are named
Triduum sacrum.
5. The Season of Easter, which is divided into Eastertide (
tempus Paschatis), Ascension (
tempus Ascensionis), and Pentecost. Eastertide runs from the Mass of the Easter Vigil to None of the Vigil of the Ascension. Ascension runs from First Vespers of the Ascension to None of the Vigil of Pentecost. Pentecost runs from the Mass of the Vigil of Pentecost to None of the Saturday following Pentecost.
6. The Season "
per annum," which runs from January 14 to None of the Saturday before Septuagesima, and also from First Vespers of Trinity Sunday to None of the Saturday before the First Sunday of Advent.
http://maternalheart.org/library/1962rubrics.pdfSo, according to the rubrics themselves, the Season of Christmas ends on January 13. Even if we were to include the time after the Epiphany, (the first season "
per annum"), Christmas would end on None of the Saturday before Septuagesima, which of course is variable.
February 2 has nothing to do with the Christmas season, liturgically speaking.