The solution I gave only resolved issues in the cron.  This error was caused by manual activation which caused the same problem.  We have a solution in 4.1.0-b1 to resolve both issues (CORE-2413).  The solution is fairly simple.  In Services::edit() (for me it is line 1158) change } else { $vars['date_last_renewed'] = $this->dateToUtc(strtotime($service->date_last_renewed . 'Z'), 'c'); to } elseif ($service->date_last_renewed) {