The names in error come from the operating system library and not from JEvents translation file. This requires the correct install of the operating system locale package.
Are you working with Linux or Windows?

The site is currently on my local computer (Windows-Apache-PHP-MySQL) and will be transferred to Linux eventually. The bulgarian translation for Joomla in general, however, seem to be working fine. The dates (month names, weekdays, etc.) appear fine on content items, for instance - 'publishing date' etc. I only get question marks with the Jevents component.

This is a Windows problem. The encoding of the names is not utf8. It will work with a correct customised Linux system. I'll put it on the task list for a workaround.

No worries. I'll test it on a Linux server.

The way your code parses the dates, however, is something to consider in the future. At the moment, the names of the weekdays appear fine on the top row of the monthly calendar view. However, when I switch to 'weekly view' they turn into question marks. Obviously, you code pulls the information about the weekdays differently, in the two different cases.

Thanks for the promt reply. This is a great extension, and I'm looking forward to its stable release.