It's each year on the 4th of December.

Barbara was living in Heliopolis in the 4th century. Her father held her prison in a tower (others say in a bath house), for he didn't want her to become christian. She was baptized anyway and led herself built an additional third window into the tower as a symbol of the holy trinity.

When her father heard about this he went to kill her, but in the tower it opened a mysterious door which transported her away to a mountain. A shepherd saw her and told her father, for which he was turned into stone.

Barbara was tortured every day and in the night the holy ghost healed all of her wounds. Right before her beheading, an angel put her in a gown white as snow. Finally her father beheaded her himself and was struck by a thunderbolt.

She is the patron saint of miners, masons and towerbuilders, architects and people who are working with explosives.

There is a tradition still alive in some parts of europe since medieval times, where on the 4th of december you cut some branches of fruit trees (forsythia works very good as well) and take them with you inside the house. 20 days later they will flower on the day of christmas.

This of course only makes sense if you are living in a region of temperate climate of the northern hemisphere.