order of date column in custom post type

That’s the only thing there is to do: array manipulation.

The filter manage_edit-CPT_columns is fired in class-wp-list-table.php:

add_filter( "manage_{$this->screen->id}_columns", array( &$this, 'get_columns' ), 0 );

Which in turn dispatches the function get_columns() in the sub-class class-wp-posts-list-table.php.

And, inside it, one filter for taxonomies, and others for post/page/cpt columns.
And all of them dealing with array elements.
Maybe a one line solution exists with some PHP function, but two lines is valid code too.