Wrong Calendar Localization

I've added a new language to my application and trying to run 1C:Enterprise with this non-english language. The built-in calendar stays the same (Sun Mon Tue...). Please assist. What is the problem?

Please check your Infobase Regional Settings (in Designer menu: Administration – Infobase Regional Settings). There is Use regional settings from the current session flag. If it is set the platform will use your computer’s regional settings to determine numbers and dates formats as well as the calendar form. If it is not set the language (Country) and other fields values in the Infobase Regional Settings form are used to determine the regional settings.