Plone 5 default theme folder_contents view come with a friendly datetime format (e.g: last 3 days) instead of exact calendar time. However there is no simple setting to display normal datetime instead of friendly datetime. After couple of hours digging around, I figured out that all folder_contents view is now handled by the mockup framework and all configurations are defined in a javascript file at "/eggs/mockup-2.1.5-py2.7.egg/mockup/patterns/structure/pattern.js" . In that file there is an option called "momentFormat":"relative" which is the configuration you need to change. In order to override this you need to:
goto: /@@resourceregistry-controlpanel
tabs: "Pattern Options"
Add pattern with name "structure" (like the name defined in the javascript five above)
content of the pattern should be '{"momentFormat": "calendar"}'
I just fixed this bug in Plone 5.1 master a few days ago to use normal date and time in folder_contents (and fixed the pattern to use localized dates) in master of 5.1, but not in b2 release.
For content management tasks the relative annoyed any editor, so I consider this a bug.