Ввести любую дату (день, месяц, год вводятся по отдельности) и вывести следующую за ней дату.

int month,day,year;
cout << "Enter date:" << endl;
cin >> year >> month >> day;
bool correct=false;
if (month > 0 && month <= 12)
{

switch (month)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:

if (day <= 31)

correct=true;

break;

case 2:

if ((day <= 29 && year % 4 == 0) || (day <= 28 && year % 4 != 0))

correct = true;

break;

case 4:
case 6:
case 9:
case 11:

if (day <= 30)

correct = true;

break;

default:

break;

}

}

if (!correct)

cout << "Incorrect date!" << endl;

else
{

if (day == 31 && month == 12)
{

day = 1;
month = 1;
year++;

}
else if (

(day == 31 && (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10))
|| (day == 30 && (month == 4 || month == 6 || month == 9 || month == 11))
|| (month == 2 && (day == 28 || day == 29))
)

{

month++;
day = 1;

}
else

day++;

cout << day << " day " << month << " month " << year << " year" << endl;

}