I want to create a wordpress user registration function so that both user and admin should get email alert after every year

I get all the users. If for any users whose expiration date is coming close to 365 he/she should get an email alert 15 days before to their registered mail ids.

With this function I am able to get the right result for 1st Year But from the next year on-wards the user registration date will be same so it wont be calculating with 365 days.

I don’t know what to do. Please Help Me on this.

  <?php

            if (!function_exists('nopaymentmade')) {

                function nopaymentmade($user_id) {
                    $blogusers = get_users('role=paid-membership');
                    // Array of WP_User objects.
                    foreach ($blogusers as $user) {

                        //$user->user_registered;
                        // $user_id=$user->ID;
                        $user->user_registered;

                        $user_id = $user->ID;

                        $user_login = $user->user_login;

                        $user_email = $user->user_email;

                        $devabirthdate = $user->user_registered;

                        /* input birthday date format -> Y-m-d */
                        list($y, $m, $d) = explode('-', $devabirthdate);
                        $nowdate = mktime(0, 0, 0, date("m"), date("d"), date("Y"));
                        $nextbirthday = mktime(0, 0, 0, $m, $d, date("Y"));

                        if ($nextbirthday < $nowdate)
                            $nextbirthday = $nextbirthday + (60 * 60 * 24 * 365);

                        $daycount = intval(($nextbirthday - $nowdate) / (60 * 60 * 24));

                        //echo $daycount; 

                        if ($daycount < 349) {

                            /* echo $user->user_registered;
                              echo "<br/>";
                              echo $user_id=$user->ID;
                              echo "<br/>";
                              echo $user_login=$user->user_login;
                              echo "<br/>";
                              echo $user_email=$user->user_email;
                              echo "<br/>"; */

                            $message = sprintf(__('your Account will be expired in next 15 days %s:'), get_option('blogname')) . "rnrn";
                            $message .= sprintf(__('Username: %s'), $user_login) . "rnrn";
                            $message .= sprintf(__('E-mail: %s'), $user_email) . "rn";

                            @wp_mail(
                                            $user_email, sprintf(__('[%s] Account Expiration alert'), get_option('blogname')), $message
                            );
                        }
                    }
                }

?>