The Twelve Days of Christmas extend the Christmas celebration until the eve of the Epiphany (Twelfth Night). This Octave plus Four is unique in the calendar of the Western Rite. In a manner of speaking, it is an Octave of Octaves.
The Octave Day of Christmas is January 1, the Feast of the Circumcision, the Eighth Day of Christmas.
St. Stephen's, St. John's and Holy Innocents' days are the second, third and fourth days of Christmas. Traditionally, these three days were also celebrated with octaves of their own - on the ninth, tenth and eleventh days of Christmas.
Lutherans usually do not mark the fifth, sixth and seventh days of Christmas. With respect to Pastor William Cwirla, there are three martyrs days within the Twelve Days of Christmas. In addition to St. Stephen and the Holy Innocents, St. Thomas of Canterbury (Becket) is on the fifth day of Christmas. At the instigation of King Henry II, he was murdered in his cathedral on December 29, 1170.
The seventh day of Christmas is St. Sylvester, Bishop of Rome, when Constantine, the first Christian emperor, put an end to persecutions and established Christianity as the religion of the empire. Sylvester, through his representatives, presided at the council of Nicea (A.D. 325). He died A.D. 335.
December 30, the sixth day of Christmas, is the only feria during the Twelve Days. Usually this day is observed with the propers assigned to the Sunday within the Octave of Christmas, even if it does not fall on Sunday.
This, then, is how Christmas is celebrated as an Octave plus Four - The Twelve Days of Christmas.