Corpus Christi — June 11 or 14, 2009

In 1264 the Pope established this feast day for the Western Church to celebrate the institution of the Eucharist. It had previously been established as a local celebration in Belgium in 1246. Of course, we regard the Last Supper as the occasion when that happened, but since that is commemorated during Holy Week, with its emphasis on the sufferings, death and resurrection of Jesus, it was decided that it would be good to have another day on which there could be an unmitigated celebration of Jesus' gift to the Church of the sacrament of his Body and Blood.

It has been traditional to have an outdoor procession on the day. Here is what Pope Benedict said on the occasion last year. And here is Pope John Paul II's reflection from 2004.

One remarkable feature of the feast is that several texts for the day were written by the great philosopher and theologian, St. Thomas Aquinas, as noted in an article about the saint in the Catholic Encyclopedia.

The day for the celebration in the Roman Calendar is the Thursday after Trinity Sunday, which is June 11 this year. But national bishops' conferences have the authority to shift it to the following Sunday; and the bishops of the United States have done so.

Here's an article from the Catholic Encyclopedia, full of unfamiliar names and terminology. And here's a more readable article from a contemporary website.