Auto create post title in admin

the_title filter filters the existing title when it’s output on the front end. If you want to set a title when a post is created on the back end, you want to use the title_save_pre filter:

function wpa65253_time_title( $title ) {
    global $post;
    if ( isset( $post->ID ) ) :
        if ( empty( $_POST['post_title'] ) && 'time' == get_post_type( $post->ID ) )
            $title="sample headline";
    endif;
    return $title;
}
add_filter ( 'title_save_pre', 'wpa65253_time_title' );