I put this code in my functions file:
add_action('acf/save_post', 'test_update_post_date_from_acf', 20);
function test_update_post_date_from_acf($post_id) {
// remove this filter to prevent potential infinite loop
remove_filter('acf/save_post', 'test_update_post_date_from_acf', 20);
// date format must be "Y-m-d H:i:s"
$post_date = get_field('email_scheduled_date');
$post = wp_update_post(array(
'ID' => $post_id,
'post_date' => $post_date));
}
And I made sure that my datepicker return format is set to: Y-m-d H:i:s