EXPLAIN
SELECT DATEDIFF('2008-12-31', '2009-01-01'), DATEDIFF('2008-03-01', '2008-02-28'),
       DATEDIFF('2007-03-01', '2007-01-28'), DATEDIFF('2008-03-01 23:59:59', '2008-03-02 00:00:00'),
       DATE_ADD('2008-12-31', 1), DATE_ADD('2008-12-31', 365),
       DATE_ADD('2008-02-28', 2), DATE_ADD('2009-02-28', 2),
       DATE_ADD('2007-02-28', 365), DATE_ADD('2007-02-28 23:59:59', 730),
       DATE_SUB('2009-01-01', 1), DATE_SUB('2009-01-01', 365),
       DATE_SUB('2008-02-28', 2), DATE_SUB('2009-02-28', 2),
       DATE_SUB('2007-02-28', 365), DATE_SUB('2007-02-28 01:12:34', 730)
       FROM src WHERE src.key = 86;

SELECT DATEDIFF('2008-12-31', '2009-01-01'), DATEDIFF('2008-03-01', '2008-02-28'),
       DATEDIFF('2007-03-01', '2007-01-28'), DATEDIFF('2008-03-01 23:59:59', '2008-03-02 00:00:00'),
       DATE_ADD('2008-12-31', 1), DATE_ADD('2008-12-31', 365),
       DATE_ADD('2008-02-28', 2), DATE_ADD('2009-02-28', 2),
       DATE_ADD('2007-02-28', 365), DATE_ADD('2007-02-28 23:59:59', 730),
       DATE_SUB('2009-01-01', 1), DATE_SUB('2009-01-01', 365),
       DATE_SUB('2008-03-01', 2), DATE_SUB('2009-03-01', 2),
       DATE_SUB('2007-02-28', 365), DATE_SUB('2007-02-28 01:12:34', 730)
       FROM src WHERE src.key = 86;