Today, of course. Here’s a history of the feast:

This feast dates back to the 12th century. It was especially promoted by the Cistercians and the Servites, so much so that in the 14th and 15th centuries it was widely celebrated throughout the Catholic Church. In 1482 the feast was added to the Missal under the title of "Our Lady of Compassion." Pope Benedict XIII added it to the Roman Calendar in 1727 on the Friday before Palm Sunday. In 1913, Pope Pius X fixed the date on September 15. The title "Our Lady of Sorrows" focuses on Mary’s intense suffering during the passion and death of Christ. "The Seven Dolors," the title by which it was celebrated in the 17th century, referred to the seven swords that pierced the Heart of Mary. The feast is like an octave for the birthday of Our Lady on September 8th.

Two reflections from bloggers:

The Anchoress

and, in a slight change of pace, the German Shepherd at the Delia Gallagher Admiration Society remembers his own mother, who died on this date. He still can’t leave Delia out of it though…