c++或c 中运行日历时出错

Question

运行日历时日期显示错误，如图所示
可能有问题的代码： case 2 :
printf("Enter month and year (MM YYYY) : ");
scanf("%d %d",&date.mm,&date.yy);
system("cls");
while(ch!='q'){
printMonth(date.mm,date.yy,20,5);
ch = getch();
if(ch == 'n'){
increase_month(&date.mm,&date.yy);
system("cls");
printMonth(date.mm,date.yy,20,5);
}else if(ch == 'p'){
decrease_month(&date.mm,&date.yy);
system("cls");
printMonth(date.mm,date.yy,20,5);
}else if(ch == 's'){
showNote(date.mm);
system("cls");
}
}