Today is Santa Lucia (Saint Lucy)'s day.
This is what Wikipedia says:
Saint Lucy's Day or the Feast of St. Lucy (Santa Lucia, Saint Lucia or sometimes Lucia forshort) is the Church feast day dedicated to St. Lucy and is observed on December 13. It retains traditional forms of celebration mainly in Scandinavia, parts of the United States and southern Europe. It is celebrated in Sweden, Denmark, Latvia, Estonia, Norway, Finland, Malta, Italy, Bosnia, Iceland, Bavaria and Croatia. In the United States, people in areas of Minnesota, and other states with Scandinavian roots, continue to celebrate the holiday, often centered around church events. Before the reform of the Gregorian calendar in the 16th century, St. Lucy's Day fell close to the winter solstice in the Northern Hemisphere. In Scandinavia this was also the date in the Gregorian calendar earlier celebrated by the heathen population that was afraid of Lucifer, a celebration that still somewhat lives today through the tradition of Lucevaka – to stay awake on the night between 12th till 13th and guard oneself against being taken by Lucifer lord of darkness by having an all night party. This is still carried out today mostly by the younger population having great parties. When the light then arrives with the morning you are safe again. In traditional celebrations, Saint Lucy comes as a young woman with lights and sweets. It is one of the few saint days observed in Scandinavia. In some forms, a procession is headed by one girl wearing a crown of candles (or lights), while others in the procession hold only a single candle each.
Here's a video from Sweden. Usually this is mainly an event for younger kids, but the song is the same.