*PROBABLY* what you want is a UNION:
SELECT * FROM audi
SELECT * FROM bmw
ORDER BY `date` DESC
But to do that *ALL* the fields in the two tables must be in the same order and have the same data type.
If that's not the case, then you need to select the fields individually:
SELECT number1, text2, text3, date4 FROM audi
SELECT numberA, textB, textC, dateD FROM bmw
ORDER BY date4 DESC
Notice that you use only ONE ORDER BY. it will mix the tables and put the results in order by date.
I also need to comment: If your two tables really are identical in structure (same fields, same types, etc.), then more than likely you made a mistake in your database design and you should have had only one common table, not two. Having two identical tables is usually
a sign of a beginner's mistake.