Any idea how to fix the SpiffyCal layout? I'm assuming this has to do with the new Bootstrap based Admin style or the updates to the calendar javascript in 1.5.6a, but when attempting to choose a custom date, the calendar goes off the left side of the screen and browser doesn't allow scrolling to the left.

ZenCart 1.5.6a
PHP 7.1

Tested in Firefox 65, Chrome 72, MS Edge
Attachment 18358