February 14, 869 and 6 April 885
Bulgaria, Czech Republic (including Bohemia, and Moravia), Ecumenism, unity of the Eastern and Western Churches, Europe, Slovakia
Formerly the feast of Saints Cyril and Methodius was celebrated in Bohemia and Moravia on 9 March; but Pius IX changed the date to 5 July. Leo XIII, by his Encyclical "Grande Munus" of 30 September, 1880, extended the feast to the universal Church.
(Taken from Catholic Encyclopedia)