In all extension language files (english.php, russian.php and all translations) in lines 16-24, 671, 672 and 675, in word CALENDAR, Latin letter C (ASCII 0x43) is misplaced with Cyrillic letter S (UTF-8 0xD0 0xA1) ... witch looks exactly as Latin C to humans.
This may lead to unexpected behavior.
Bug is not limited to extension nor to listed lines.
Regards,
Filip