Certain high-ranking feasts in the Church's calendar can be celebrated on Sundays, while others are bumped to the next day.
In the Catholic Church, Sundays are usually celebrated according to the season of the liturgical year, such as Ordinary Time.
However, on certain occasions the seasonal Sunday celebration is replaced by a feast.
This doesn't happen often, but it can when the following criteria are met.
To give a few examples, here are a few feasts and solemnities that can be celebrated on a Sunday.
There are others not listed here, but this gives a brief survey of the various feasts in the Church's year that are on fixed days. When that day is on a Sunday, it can replace the typical seasonal celebration.
