Add a method to DateFormat enum to give a dateformat that works directly with datetime library

**Is your feature request related to a problem? Please describe.**
Need to have a quick input to the datetime string

Would like to have
```
date_enum = DateFormatEnum.DD_MM_YYYY
date_enum.string_format = "%d/%m/%Y"
```

Locate DateFormatEnum and its existing date-format members, then inspect how datetime strings are currently handled. Confirm the intended interface for DD_MM_YYYY and verify that the enum value provides a format usable directly with the datetime library. Done means the requested format works without manual setup and is covered by the relevant tests.

Written by the indexing model from the issue text.