```sql
EXPLAIN SELECT unix_timestamp(publish_date) as publish_date
    -> FROM vpt_program
    -> WHERE language = 'en' and publish_date <= '2013-10-02'
    -> ORDER BY publish_date DESC
    -> LIMIT 1;
+----+-------------+-------------+------+----------------------+---------+---------+-------+------+------------------------------------------+
| id | select_type | table       | type | possible_keys        | key     | key_len | ref   | rows | Extra                                    |
+----+-------------+-------------+------+----------------------+---------+---------+-------+------+------------------------------------------+
|  1 | SIMPLE      | vpt_program | ref  | program,publish_date | program | 4       | const |    1 | Using where; Using index; Using filesort |
+----+-------------+-------------+------+----------------------+---------+---------+-------+------+------------------------------------------+
1 row in set (0.00 sec)
```
Maybe PHP strtotime function is better option here?

```sql
EXPLAIN SELECT publish_date FROM vpt_program WHERE language = 'en' and publish_date <= '2013-10-02' ORDER BY publish_date DESC LIMIT 1;

+----+-------------+-------------+------+----------------------+---------+---------+-------+------+--------------------------+
| id | select_type | table       | type | possible_keys        | key     | key_len | ref   | rows | Extra                    |
+----+-------------+-------------+------+----------------------+---------+---------+-------+------+--------------------------+
|  1 | SIMPLE      | vpt_program | ref  | program,publish_date | program | 4       | const |    1 | Using where; Using index |
+----+-------------+-------------+------+----------------------+---------+---------+-------+------+--------------------------+
1 row in set (0.00 sec)
```