could you @avjoomla test if the fix solves the problem

Release Blocker?

@infograf768 we need to test and merge before release

Tested that it does not break the new calendar (just to be sure). I do not have a sample code to test the original issue.

Added release blocker tag

Just installed a new installation of Joomla! 3.7 as released today.
Sadly there are to typos in the code which was merged into the behavior.php with PR #15441

Line 381 (wrong)
JHtml::('stylesheet', 'system/calendarjos.css', array('version' => 'auto', 'relative' => true), $attribs);
correct:
JHtml::('stylesheet', 'system/calendar-jos.css', array('version' => 'auto', 'relative' => true), $attribs);

Line 383 (wrong)
JHtml::('script', $tag . '/calendarsetup.js', array('version' => 'auto', 'relative' => true));
correct
JHtml::('script', $tag . '/calendar-setup.js', array('version' => 'auto', 'relative' => true));

In both cases the file name is incorrect, the minus characters in file names are missing.

Regards,
Aicha

Can you please send that as PR against staging?