Problem/Motivation
On #2393339: [META] Make sure Views base fields are using Field API for formatting, and do not lose functionality we are updating all uses of entity-unaware formatters for entity base fields to use formatters that are entity-aware.
This issue is about the date/time fields.
Proposed resolution
Update the 'date' plugin ( \Drupal\views\Plugin\views\field\Date ) where it is used in the base EntityViewsData class to use a Field UI formatter instead.
Related issue: #2399211: Support all options from views fields in timestamp formatters updates the Field UI timestamp formatter to include all the options present in Views timestamp formatters.
Remaining tasks
Make a patch.
User interface changes
Not really.
API changes
Entity date fields will use Field UI to format instead of generic Views formatters.