Today, January 5th is the 12th day of Christmas! Twelvetide, or Christmastide, dates as far back as the sixth century.
January 6th, or "Epiphany" is celebrated to mark the day the wise men (or kings) came to honor Christ with gifts. Though Jesus was likely born in the spring, this season is used for traditional & liturgical celebration.
Advent is the days leading up to Christmas. Christmastide is the 12 days from Dec 25 to Jan 5. Then, if you live in New Orleans or Rio, begins the carnival season that culminates in Mardi Gras which is the day before Ash Wednesday.