What carol mentions a 19th century Duke of Bohemia?

The carol that mentions a 19th-century Duke of Bohemia is "Good King Wenceslas." The song tells the story of King Wenceslas I of Bohemia, who was known for his generosity and compassion towards the poor. Although he lived in the 10th century, the song's popularity rose in the 19th century, which may lead to confusion regarding the timeline. The carol highlights themes of charity and kindness during the winter season.