Congratulations to all colleagues on the holiday!
The Day of Bulgarian Alphabet, Bulgarian Enlightenment and Culture (Bulgarian: Ден на българската просвета и култура и на славянската писменост) has been celebrated in Bulgaria since 11 May 1851 (old style). Today, this holiday is celebrated every year on May 24th (new style) and is an official holiday of Bulgaria since 1990. In 2020, the name was changed to “Day of the holy brothers Cyril and Methodius, of the Bulgarian alphabet, education and culture and of Slavic literature”.
Cyril and Methodius had been saints since the 9th century, and the commemoration of their saint's day had been celebrated in Bulgaria since the 12th century.
Similar days celebrating Slavic writing and culture are observed in North Macedonia, Russia and Serbia.