message: Update day-of-the-week.cpp
diff: @@ -13,7 +13,7 @@ public:
  --year;
  }
  int c = year / 100, y = year % 100;
  - const auto& w = ((y + y / 4 + c / 4 - 2 * c + 13 * (month + 1) / 5 + day - 1) % 7 + 7) % 7;
  + const auto& w = ((c / 4 - 2 * c + y + y / 4 + 13 * (month + 1) / 5 + day - 1) % 7 + 7) % 7;
  return DAYS[w];
  }
  };
  