It probably doesn't mean anything to you, but it's a special day in Bulgaria. It's Bulgarian Education and Culture, and Slavonic Literature Day.
Anyway, google changed their name as it's written in Bulgarian (cyrillic).
You may see that from here:
http://google.bg
No other google website (i.e. google.cn) has done this for any other country. :D
If you're curious about this day, there is info in English:
http://en.wikipedia.org/wiki/Saints_Cyril_and_Methodius_Day#Saints_Cyril_and_Methodius_Day