December 26

First, the reason for the feast day.  It commemorates Stephen, the first martyr of the church:

54 When they heard these things, they became enraged and ground their teeth at Stephen. 55 But filled with the Holy Spirit, he gazed into heaven and saw the glory of God and Jesus standing at the right hand of God. 56 “Look,” he said, “I see the heavens opened and the Son of Man standing at the right hand of God!” 57 But they covered their ears, and with a loud shout all rushed together against him. 58 Then they dragged him out of the city and began to stone him; and the witnesses laid their coats at the feet of a young man named Saul. 59 While they were stoning Stephen, he prayed, “Lord Jesus, receive my spirit.” 60 Then he knelt down and cried out in a loud voice, “Lord, do not hold this sin against them.” When he had said this, he died.  (Acts 7:54-60)

We remember this, if at all, because of the song:

Good King Wenceslas looked out
On the feast of Stephen,
When the snow lay round about
Deep and crisp and even;

Brightly shone the moon that night
Though the frost was cruel,
When a poor man came in sight,
Gath'ring winter fuel.

'Hither, page, and stand by me,
If thou know'st it, telling
Yonder peasant, who is he?
Where and what his dwelling?'

'Sire, he lives a good league hence,
Underneath the mountain,
Right against the forest fence,
By Saint Agnes' fountain.'

'Bring me flesh and bring me wine,
Bring me pine logs hither,
Thou and I will see him dine
When we bear them thither.'

Page and monarch forth they went,
Forth they went together,
Through the rude wind's wild lament
And the bitter weather.

'Sire, the night is darker now
And the wind blows stronger;
Fails my heart, I know not how,
I can go no longer.'

'Mark my footsteps, good my page,
Tread thou in them boldly:
Thou shalt find the winter's rage
Freeze thy blood less coldly.'

In his master's steps he trod,
Where the snow lay dinted;
Heat was in the very sod
Which the Saint had printed.

Therefore, Christian men, be sure
Wealth or rank possessing,
Ye who now will bless the poor
Shall yourselves find blessing.

Which, if turns out, was written in 1853 to a 13th century tune.

The carol was written for the Feast of St Stephen, better known as Boxing Day. And it celebrates the long tradition of charitable giving on the Second Day of Christmas.

That "long tradition" is something else we've lost in America, thanks to the Puritans who despised Christmas and all traditions surrounding it.  As for Wenceslaus, he had a rough time of it:

Duke, martyr, and patron of Bohemia, born probably 903; died at Alt-Bunzlau, 28 September, 935.

His parents were Duke Wratislaw, a Christian, and Dragomir, a heathen. He received a good Christian education from his grandmother (St. Ludmilla) and at Budweis. After the death of Wratislaw, Dragomir, acting as regent, opposed Christianity, and Wenceslaus, being urged by the people, took the reins of government. He placed his duchy under the protection of Germany, introduced German priests, and favoured the Latin rite instead of the old Slavic, which had gone into disuse in many places for want of priests. Wenceslaus had taken the vow of virginity and was known for his virtues. The Emperor Otto I conferred on him the regal dignity and title. For religious and national motives, and at the instigation of Dragomir, Wenceslaus was murdered by his brother Boleslaw. The body, hacked to pieces, was buried at the place of murder, but three years later Boleslaw, having repented of his deed, ordered its translation to the Church of St. Vitus in Prague. The gathering of his relics is noted in the calendars on 27 June, their translation on 4 March; his feast is celebrated on 28 September.

There's a surprising amount of death on the Christian calendar after the celebration of the birth of the Christ-child.  It's almost a reminder that "peace on earth, goodwill toward" all, is not so much a gift as a hope that we have some part in.