# replace first argument of STR_TO_DATE with value from PHP/frontend
TIME( STR_TO_DATE( '10:00 PM','%h:%i %p' ) );

选择：

# replace first argument with your time field
TIME_FORMAT( '22:00:00','%h:%i %p' );

编辑：
我将继续并假设你使用MysqL lib函数.

// first sanitize the $_POST input
// also,make sure you use quotes to identify the $_POST keys
$open = MysqL_real_escape_string( $_POST[ 'MondayOpen' ] );
$close = MysqL_real_escape_string( $_POST[ 'MondayClose' ] );

// this is the query,which should work just fine.
$sql = '
    INSERT INTO
        `table_lib_hours`
    SET
        `day_name` = "Monday",`day_open_time` = TIME( STR_TO_DATE( "' . $open . '","%h:%i %p" ) ),`day_close_time` = TIME( STR_TO_DATE( "' . $close . '","%h:%i %p" ) )
    ';

$result = MysqL_query( $sql );

然后检索值：

$sql = '
    SELECT
        `day_open_time`,`day_close_time`,TIME_FORMAT( `day_open_time`,"%h:%i %p" ) as day_open_time_formatted,TIME_FORMAT( `day_close_time`,"%h:%i %p" ) as day_close_time_formatted
    FROM
        `table_lib_hours`
    WHERE
        `day_name` = "Monday"
    ';

$resultset = MysqL_query( $sql );

这将返回结果集,其中格式化数据位于* _formatted字段中

编辑：调整后的％m(月)到％i(分钟).感谢Donny发现了一个很好看的漏洞.