Problem with calendar and change the language of birthdays in the home page

Hello!
I want to report a problem with the calendar on my forum if someone can look for what this is about. And is it possible on the homepage where noted birthdays of users here (No users have a birthday today
No users are having a birthday in the upcoming 1 days) to change the language from English to Bulgarian?
Thanks in advance!
http://colorforum.bulgarianforum.net

admin panel>general>Forum>Configuration>default Language>Bulgarian(but i dont think there is bulgarian)

Thanks for this response- Cool-processor , but unfortunately it is not satisfactory for me: (
This inscription (No users have a birthday today
No users are having a birthday in the upcoming 1 days) I go to the home page as English, and I want to be a Bulgarian. And how can I fix the calendar on the homepage too, because it shows me the error?
Please help and hope to get one, count on you.