Programmatically set post date using wp_insert_post

Hi,

When programmatically creating a post, I am trying to set the post date, eg:

$my_post = array(
		'post_title'    => wp_strip_all_tags( $item_title ),
		'post_content'  => $post_content,
		'post_status'   => 'publish',
		'post_author'   => 1,
		'post_date' => $postdate
		);
wp_insert_post( $my_post );

And I am not able to set the post date programmatically.

If I hardcode the date, this does work:

$postdate = "2010-02-23 18:57:33";

But if I try to use a variable I cannot get it to work, even though both seem to contain exactly the same format and type:

echo of hardcoded $postdate:

2010-02-23 18:57:33 string

echo of $postdate if I get the date programmatically:

2021-02-06 13:07:03 string

Any help is very much appreciated.