On which Christian feast day was the Sistine Chapel first consecrated?

The Sistine Chapel was first consecrated on the Feast of the Assumption.

The Feast of the Assumption celebrates the belief that Mary, the mother of Jesus, was taken bodily into heaven. It is observed on 15 August in Western Christianity, making the date especially appropriate for a chapel dedicated to the Virgin Mary.

Pope Sixtus IV consecrated the newly built chapel in 1483. The ceremony took place before the later decoration that made the building world-famous, including Michelangelo’s ceiling and The Last Judgment on the altar wall.

The feast should not be confused with the chapel’s construction date or with the dates of its major frescoes. The building’s name honors Sixtus IV, while its original dedication connected it closely with Marian worship and the liturgical calendar.