October 3 is the vigil of St. Francis of Assisi's death and bears a special name the Transitus.
Be praised, my Lord, through our Sister Bodily Death, from whose embrace no living person can escape. Woe to those who die in mortal sin! Happy those she finds doing your most holy will. The second death can do no harm to them. St. Francis of Assisi, Canticle of the Creatures.
Death dates are commonly celebrated in the Church. In fact, every day on the calendar is dedicated to a relatively small handful of saints. This is due to the fact that we have thousands of saints and beati but only 365 days (and 366 every now and again) on our calendar. That means there's definitely going to be some doubling up. Even Christmas, one of the holiest days on our liturgical calendar, isn't safe. In fact, St. Anastasia of Sirmium, an early and very important Christian martyr, has the second Mass on Christmas morning dedicated to her.
That's pretty cool beans considering she's sharing top billing with the Our Lord Himself.
Please visit a Franciscan Parish or a Diocesan Church tonight that may be celebrating this holy saint's death. It is not a mass, it's a service.