code: public static function checkLeapYear($year)
      {
          $year = Cast::_Int($year);
  
          if ($year % 4 !== 0) {
              return false;
          } elseif ($year % 100 !== 0) {
              return true;
          } elseif ($year % 400 !== 0) {
              return false;
          } elseif ($year === 0) {
              return false;
          }
  
          return true;
      }
docs: True if it's a leap year
  
  @param  int  $year
  @return bool