The date (and time) value is displayed in the nls_date_format. If you want to test procedure xyz and display date variables with a specific format, you can simply modify your test script like this:
Code
begin
-- Modify the nls_date_format for this session
dbms_session.set_nls(param => 'nls_date_format',
value => '''DD-MM-YYYY HH24:MI:SS''');
-- Run the procedure
xyz(p1 => :p1, p2 => :p2);
end;