mysql - Error while partitioning. [Err] 1654 - Partition column values of incorrect type -

what's wrong mysql query?
result [err] 1654 - partition column values of incorrect type

drop table if exists part; create table `part` (   `id` int(11) not null auto_increment,   `cnt` varchar(255) default null,   `created` datetime not null,   primary key (`id`, `created`) ) engine=innodb default charset=latin1  partition range columns (created)(     partition p_2015_01 values less ('2015-01-30') engine=innodb,     partition p_2015_02 values less ('2015-02-30') engine=innodb,     partition p_2015_03 values less ('2015-03-30') engine=innodb,     partition p_catchall values less (maxvalue) engine=innodb ); 

if matters, version 5.5

it took quite long time see obvious:

the date '2015-02-30' not exist.

presumably converted null or something, therefore message 'incorrect type'.

hopefully helps someday.