Slovakia Method: July 5th on Gregorian calendar Length: 1 day Period: 1 year More Information Saints Cyril and Methodius Day Saints Cyril and Methodius ( Greek : Κύριλλος καὶ Μεθόδιος , Old Church Slavonic : К ѷ риллъ и Ме ѳ одїи [more] ) were Byzantine Greek brothers born in Thessaloniki