How can I change the publish date based on a custom field?

I don’t know how your front end form saves its data, but presumably it is using wp_insert_post and wp_update_post. If so, there is a filter called wp_insert_post_data that can be used to alter the post data before the post is inserted or updated.

function reset_post_date_wpse_100021($data,$postarr) {
  var_dump($data,$postarr); die; //debug
  // your code
  return $data;
}
/**
 * runs before new posts have IDs !!!
 */
add_filter('wp_insert_post_data','reset_post_date_wpse_100021',99,2);

The second parameter is your $_POST data plus the old database data with the $_POST data overwriting the old data where they conflict.

If you look at the var_dump of that $postarr value you should see your datepicker data. You need to chop up your datepicker data and overwrite the date values in the $data array.

The issue I see is that WordPress (and MySQL) uses 0000-00-00 00:00:00— Y-m-d H:i:s— as the datetime format. That is what you need to provide, but you don’t mention a time component at all. At the very least tack 00:00:01 onto your date.

That should be all you need.

Related Posts: