Case object in Salesforce is a bit different and special compare to other objects. There are additional fields such as Date/Time Opened and Date/Time Closed.
The Date/Time Opened field value is the same as the Created Date field in other objects, this field can be added to the case page layout.
The Date/Time Closed field is auto-populated when the case status is changed to system Closed, this field can be added to the case page layout too, but the field is not available for history tracking.
In the report, there are additional fields available as screenshot below:
Each pair have the date time field and date only field:
1. Date/Time Opened with Opened Date
2. Date/Time Closed with Closed Date
3. Case Date/Time Last Modified with Case Last Modified Date
But, the Created Date field will not available for reporting in Case.
Date/Time Closed field
As mentioned above, when the case status is changed to system closed, the date/time closed field will be auto-populated as when the case is closed.
However, when the case is re-open, the value of the date/time closed field will be set to blank and populate back with when the latest case is closed.
Sample SELECT Id, CreatedDate,ClosedDate FROM case WHERE Id = '5000o00002J2JQzAAN'
The format for both fields here is date/time.