Saints Cyril and Methodios of Thessalonica, Equals-to-the-Apostles and enlighteners of the Slavic peoples.
Cyril (baptized Constantine) and his elder brother Methodios were born in Thessalonica in the ninth century. Sent by the Emperor and Patriarch Photios to Moravia, they devised an alphabet for the Slavonic language and translated the Scriptures and services, so that the Slavs might worship in their own tongue.
Cyril died in Rome in 869 and Methodios, as Archbishop of Moravia, continued the work until his repose in 885. Their disciples carried the Slavonic liturgy to Bulgaria and beyond.
Feast day
On the New Calendar, Cyril and Methodios, Enlighteners of the Slavs is commemorated on May 11. Churches on the Old (Julian) Calendar keep the feast on May 24 of the civil calendar.
Who celebrates a name day
People with these names keep their name day on this feast:
Kyrillos, Kirillos, Cyril, Kyril, Methodios, Methodius
Also commemorated on May 11

Founding of Constantinople
Saint, Εγκαίνια Κωνσταντινουπόλεως
Commemoration of the dedication of Constantinople as the New Rome by Saint Constantine the Great.
Argyrios of Epanomi
Martyr, Αργύριος ο Επανομίτης
New Martyr Argyrios of Epanomi, a young tailor hanged at Thessalonica for confessing Christ.
Olympia and Euphrosyne of Mytilene
Holy Woman, Ολυμπία και Ευφροσύνη
Venerable Martyrs Olympia and Euphrosyne, nuns of Mytilene slain by invaders.
Name days: Olympia
Dioskoros the New
Martyr, Διόσκορος ο Νέος
New Martyr Dioskoros, who suffered at Smyrna.
Name days: Dioskoros
Icon: public domain image from Wikimedia Commons.