Just FYI … just spent way too much time with this. Out of a sudden my datepickers css were screwed up this morning without having changed anything. Figured that last evening there’s been an update to the latest Version ( 6.7.27) of the Slider Revolution Plugin.
The culprit is \plugins\revslider\admin\assets\css\builder.css
There’s some datepicker classes in there (line 879) which did overwrite even orbital theme styles. Commented out and all is fine again…