Something

mysql> set @t='2007-01-01';Query OK, 0 rows affected (0.00 sec)mysql> select date_format(timediff(now(),@t),'%Y-%m-%d %H:%i:%s');+-----------------------------------------------------+| date_format(timediff(now(),@t),'%Y-%m-%d %H:%i:%s') |+-----------------------------------------------------+| NULL                                                |+-----------------------------------------------------+1 row in set, 1 warning (0.00 sec)mysql> show warnings;+---------+------+----------------------------------------------+| Level   | Code | Message                                      |+---------+------+----------------------------------------------+| Warning | 1292 | Truncated incorrect time value: '2007-01-01' |+---------+------+----------------------------------------------+1 row in set (0.00 sec)