A single Time_Image routine that takes a bunch of formatting parameters
is quite nice because you can just declare your own, with your own
preferred parameters, as a renaming.  eg
  function RFC822_Date(Time : Ada.Calendar.Time
                       Date_Format : ... := ...
                       Date_Separator : Character := '/';
                       Day_Of_Week_Format : ... := ...
                       ... ) return String
   renames Time_Image;
and then
  Ada.Text_IO.Put_Line(RFC822_Date(Now));
* See smplsrvr on www.adapower.com for an example