mysql> insert into test values ('2012-02');
Query OK, 1 row affected, 1 warning (0.36 sec)

mysql> select * from test;
+---------------------+
| xoxo                |
+---------------------+
| 0000-00-00 00:00:00 |
+---------------------+
1 row in set (0.00 sec)

mysql> insert into test values ('2012-02-08');
Query OK, 1 row affected (0.13 sec)

mysql> select * from test;
+---------------------+
| xoxo                |
+---------------------+
| 0000-00-00 00:00:00 |
| 2012-02-08 00:00:00 |
+---------------------+
2 rows in set (0.00 sec)

mysql>