Date Time MySQL

mysql>
mysql>
mysql> SELECT SUBDATE('2004-12-31 23:59:59', 31);
+------------------------------------+
| SUBDATE('2004-12-31 23:59:59', 31) |
+------------------------------------+
| 2004-11-30 23:59:59                |
+------------------------------------+
1 row in set (0.00 sec)