This is the standard placeholder text that Microsoft uses on the calendar. It is just there to signify that there is an event that day. I believe it is Latin. The problem is that with high def screens you can actually read the text! Hopefully they will eventually use actual event info on the month view calendar.
But still, the calendar month view should have been improved to make use of all those Lumia 920 pixels! This ought to come in an update soon, perhaps even with other obvious improvements to the build-in calendar, like week view, better live tile, etc.