#include<iostream> #include<algorithm> #include<string> using namespace std; void nextday(int& y, int& m, int& d) { int dayMonth[] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 }; bool isLeap = y % 400 == 0 || y % 4 == 0 && y % 100 != 0; if (isLeap) { dayMonth[2] = ...