The date (and time) value is displayed in the nls_date_format. This is an unfortunate Oracle Server behavior, the debugger doesn't even know that the variable is a date. However, if you want to test procedure xyz and display date variables with time fraction, you can simply modify your test script like this:
Code:
begin
// Modify the nls_date_format for the session of the test script
dbms_session.set_nls('nls_date_format','''DD-MM-YYYY HH24:MI:SS''');
// Run the procedure
xyz(:param1, :param2);
end;