Today is the Feast of St Teresa de Jesus, commonly called St Teresa of Ávila, but why? Saints' Feasts are normally kept on their dies natalis, or heavenly birthday, the day of their death. There are exceptions, such as keeping the Feast on the day of the Translation of their relics, however, the standard practice is day of death=day of feast.
Friday, 15 October 2021
An Odd Fact About the Feast of St Teresa de Ávila
So what is the odd fact about St Teresa? The fact that we do not know whether she died on 4 October or 15 October. What, you say!? Well, she died in 1582, just as Catholic nations were making the switch from the Julian to the Gregorian calendar, which required the removal of 5–14 October from the calendar. She died either before midnight of 4 October or early in the morning of 15 October, hence we are not sure of the date of her death.
However, since 4 October had been occupied by the Feast of St Francis of Assisi since AD 1228, her Feast Day was placed on the 15th.