mysql>
mysql> SELECT NOW( ), NOW( ) - INTERVAL 24 HOUR;
+---------------------+---------------------------+
| NOW( ) | NOW( ) - INTERVAL 24 HOUR |
+---------------------+---------------------------+
| 2011-10-03 13:05:47 | 2011-10-02 13:05:47 |
+---------------------+---------------------------+
1 row in set (0.00 sec)