Reflection from Pray as You Go - here
From Catholic Culture.org:
St. Cyril was a priest and a philosopher and accompanied his brother St. Methodius to Moravia to preach the Gospel. They both perfected a Slavonic alphabet which is now known as the Cyrillic alphabet and translated the liturgy into this language. They were summoned to Rome, where Cyril died on this date in 869, and Methodius was consecrated bishop and sent to Pannonia. He died on April 6, 885, in Velehrad, Czech Republic, after working tirelessly on spreading the Gospel.
Both brothers are venerated in the Orthodox Church as saints with the title of "equal-to-apostles". In 1880, Pope Leo XIII introduced their feast into the calendar of the Roman Catholic Church. In 1980, Pope John Paul II declared them co-patron saints of Europe, together with Benedict of Nursia. In 1999 at the Synod on Europe just before the Great Jubilee in 2000, St John Paul II also made St Bridget of Sweden, St Catherine of Siena and St Teresa Benedicta of the Cross (Edith Stein) co-patrons of Europe.
An interesting Irish connection to the two saints is that St Cyril is buried in the Basilica of San Clemente in Rome which is in the care of the Irish Dominicans.