Ajax future single post query doesn’t work when NOT logged in

usually it because you are missing an “add_action” call for none logged in users.

add this to your plugin or functions.php

add_action('wp_ajax_nopriv_REPLACETHIS', 'ajax_get_date_post');

and change the REPLACETHIS to your action value from the ajax call.

remember that when calling ajax from front-end and you want to allow none logged in users
to make these calls you allways add both:

    add_action('wp_ajax_my_action', 'my_action_callback');
    add_action('wp_ajax_nopriv_my_action', 'my_action_callback');

you can read about more at the codex