When saving a content type containing a DateAndTime field type, the following error shows if "Default value" is set to any other value than "Adjusted current datetime":

Setting 'dateInterval' can be used only when setting 'defaultType' is set to 'DEFAULT_CURRENT_DATE_ADJUSTED'

Secondary issue: The error message should be easier to understand. E.g. it should say "Adjusted current datetime" instead of "DEFAULT_CURRENT_DATE_ADJUSTED", because that's what the user sees.