return random date

function get_random_date($start_date, $end_date) {
      
      $min = strtotime($start_date);
      $max = strtotime($end_date);
      
      $val = rand($min,$max);

      return date('Y-m-d', $val);
  }
  
  get_random_date('2020-01-01', '2020-01-31')