"Little Nativity"
Herthe 11th (January 5th) is Duodecima - the Twelfth Day of Nativity. Herthe 12th (January 6th) is the High Feast of the Epiphany, popularly known as Princesses' Day.
Epiphany, the showing-forth of the new-born Daughter of Dea is often called Little Nativity, and is one of the most joyful and important festivals of the year. Read more about it here.