St Lucia's Day is celebrated on the 13th of December, very close to the Winter Solstice. It is one of the most special days in the calendar and as integral to Scandinavia as glögg and herring. One of the biggest celebrations in December, aside from Christmas, it is an annual celebration born from stories that were told about how Christianity came to Sweden.
St Lucia was a young Christian girl who was martyred, killed for her faith, in 304. The most common story told about St Lucia is that she would secretly bring food to the persecuted Christians in Rome, who lived in hiding in the catacombs under the city. She would wear candles on her head so she had both her hands free to carry things. Lucy means “light” so this is a very appropriate name.
The 13th of December was also the Winter Solstice, the shortest day of the year, in the old Julian Calendar and a pagan festival of lights in Sweden was turned into St. Lucia's Day.
On St Lucia’s Day, you can expect to see churches, town halls, schools, offices and restaurants become a twinkling sea of candlelight. The day is celebrated with a Lucia train procession in which a young girl elected to portray St Lucia leads the way wearing a white gown, with a red sash and crown of candles which is made of Lingonberry branches, evergreen symbolising new life in winter. She is trailed by Lucia handmaidens, star boys and gingerbread men who all carry candles and sing carols. The tradition dates back to the original story of Lucia, who delivered food to the persecuted Christians, leading her way with candlelight. A popular food eaten at St. Lucia's day are “Lussekatts”, S-shaped buns flavoured with saffron and dotted with raisins which are eaten for breakfast.
St Lucia's Day first became widely celebrated in Sweden in the late 1700s. St Lucia's Day is also celebrated in Denmark, Norway, Finland, Bosnia, and Croatia. In Denmark it is more a of a children's day and in some parts of Italy, children are told that St Lucy brings them presents. They leave out a sandwich for her and the donkey that helps carry the gifts.
https://www.goodcatholic.com/festival-of-light-celebrate-st-lucy-and-st-lucys-day/