Mysql function TO_SECONDS doesn't exist

Mysql function TO_SECONDS doesn't exist

I've been passing through this problem for one day, and it's hard to
understand why MySql doesn't work easily.
I'm trying to execute the statement below, but it isn't recognized at all.
SELECT TO_SECONDS('2013-09-12 11:15:00');
I get the following error:
ERROR 1305 (42000): FUNCTION db.to_seconds does not exist
I've checked MySQL's documentation and this function is available since
version 5.5. So, I updated my previous version and now I'm working with
6.0 but still not working.
mysql> select version();
+---------------------------+
| version() |
+---------------------------+
| 6.0.4-alpha-community-log |
+---------------------------+
1 row in set (0.03 sec)
Server version: 6.0.4-alpha-community-log MySQL Community Server (GPL)
Anyone knows what is going on?