为什么我的代码在输出中增加了93天

我有一个c++任务，要求输入一个日期和第二个日期，并找出两者之间的天数，包括闰年。我的代码显示了两个日期的正确值，但当测试1/2/3到3/21/1234时，它显示4507994，比4507901的正确值多93天。为什么会发生这种情况？我包括cstdlib和iostream

using namespace std;
bool isLeapYear (int year)
{
bool tf;
if (year%4 !=0)
{
tf = true;
}
else if (year%4 == 0)
{
if (year%1000 == 0)
{
if (year %400 == 0)
{
tf = false;
}
else
{
tf = true;
}
}
tf = false;
}
return tf;
}
int last_day(int month, int year)
{
int lday;
if (month == 2)
{
if (isLeapYear (year) == false)
{
lday = 29;
}
else
{
lday = 28;
}
}
else if (month == 1 || month == 3 || month == 5 || month ==  7 || month == 8|| month == 10 || month ==12)
{
lday = 31;
}
else if (month == 4 || month == 6 || month == 9 || month == 11)
{
lday = 30;
}
return lday;
}
void howlongwait (int &month, int &day, int &year)
{
if (day == last_day(month, year))
{
if (month == 12 && day == 31)
{
month = 1;
day = 1;
year = year+1;
}
else
{
month = month+1;
day = 1;
year = year;
}
}
else
{
month = month;
day = day+1;
year = year;
}
}

int main()
{
int month, month2, day2, day, year, year2;
int days = 0;
char trash, garb, garb2, trash2;
cout << "Enter start date (no spaces): " << endl;
cin >> month >> trash >> day >> garb >> year;
cout << "Enter end date (no spaces): " << endl;
cin >> month2 >> trash2 >> day2 >> garb2 >> year2;
if (year2 < year)
{
cout << "Never..." << endl;
return 0;
}
else
{
while ((month != month2) || (day != day2) || (year != year2))
{
howlongwait (month, day, year);
days=days+1;
}
}
cout << "You have to wait " << days << " days" << endl;
}

`