May 24 is the day of one of the most important Bulgarian holidays - the Day of the Slavonic Literacy and Alphabet. The reason for the holiday is that the Cyrilic script, or alphabet, was created in Bulgaria, in 10th century, possibly by Bulgarian, for sure Slavic, students of the Byzantinian monks Cyril and Methodius,
who were given as a task by Byzantium to create an alphabet that fit the language of the Slavs, so Christianity could be spread to them. St. Cyril and Methodius
http://en.wikipedia.org/wiki/Saint_Methodius created an alphabet called "Glagolitic"
http://en.wikipedia.org/wiki/Glagolitic_alphabet, on which were written the oldest Slavonic documents. It looks like that
The story goes that the Slavic prince of the Great Moravia, Rostislav, had sent a mission to Byzantium with a request to be sent Christians to evangelize his people. So, they devised the Glagolic, and after Vyril's death Methodius stayed as an archebishop in Panonia; in this time rome nd Byzantien split over "Filoque" and just after Methodius died Glagolic and the Chrsitiabn service on it was forbidden, so what was left from the students of Cyril and Methodius fled for their lives. Couple of them ended in Bulgaria, where the Bulgarian Tsar Boris I welcomed them because he hoped that their own alphabet will secure some independence of his people from the cultural influence of Byzantium. Those students created the Cyrilic out of the Glagolic, which became the alphabet for a good deal of nations, like Bulgaria, Russia, Macedonia, Kazahstan, Mongolia, it's used in Serbia, etc.
The fact that Cyrilic has been developed and first used in Bulgaria has always been a source of pride for all Bulgarians, and this day is celebrated in most joyful way. It became day on which literature, education, knowledge itself was and is celebrated, with festivals, manifestations /in my communist youth/, speeches of important people and professionals in the spheres of education.
Here a short history of the holiday:
"...On May 11 1851 a celebration was organized by Nayden
Gerov at the eparchy school `St St Kiril and Methody` in the town of
Plovdiv. This was the first time to be marked the Day of the Saint
brothers Kiril and Methody – the creators of Slavonic Alphabet. Since
1857 this day has been celebrated every year in Plovdiv, Tsarigrad,
Shumen and Lom and it was no by accident that May 11 was chosen - this
is the common Church Holiday of the two Saints.
The earliest information for marking the 11th of May a
day of the Saint Apostles and Slavonic enlighteners Kiril and Methody
dates back to XII century, but they were already acknowledged for saints
at the time of IX century. Tthe memory of St Kiril only is celebrated
on 14th February and the memory of his brother St Methody - on 6th of
April (the exact dates of their deaths).
The wholly Russian Synod took the following decision
on the occasion of celebrating one thousand years form the Moravia
mission of St St Kiril and Methody: ` To remember the millennium since
the first time our paternal language has been illuminated by the Gospel
and the Christen faith, let it be established to be a Church Holiday the
Day of the Reverends Kiril and Methody and celebrated every year,
starting from the present May 11, 1863! `. Since then that Day has been
celebrated in all of the Orthodox Slavonic countries. The common Day of
St St Kiril and Methody was also celebrated by Bulgarian Church in the
next centuries, and through Bulgarian Revival period it became also the
Day of the School and the letters created by Kiril and Methody.
This occasion was one that was giving the expression
of Bulgarian strivings of spirit for Church and Political independence,
for enlightenment and national rise. Through the Revival period the Day
of St St Kiril and Methody was celebrated not only in Bulgaria, but also
abroad – by Bulgarian revival immigrates in Rumania and Russia, among
Bulgarian students in foreign lands, among Bulgarians exiled in
Diarbekir...." http://www.balkanfolk.com/news.php?id=23