#include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> int year, month, day; const int day_30 = 30; const int day_31 = 31; int day_month_2 = 0; char err_flag = 0; void compute() {  printf("输入年月日(1992-7-19)：");  scanf("%d-%d-%d",&year, &month, &day);  if((year%4==0 && year0!=0) || (year%400==0))  {   day_month_2 = 29;  }  else  {   day_month_2 = 28;  }  if(month>=1 && month<=12)  {   if(month == 2)   {    if(day > day_month_2)    {     err_flag = 1;    }    else if(day == day_month_2)    {     month++;     day = 1;    }    else    {     day++;    }   }   else if(month==1 || month==3 || month==5 || month==7 ||\     month==8 || month==10 || month==12)   {    if(day > day_31)    {     err_flag = 1;    }    else if(day == day_31)    {     month++;     day = 1;    }    else    {     day++;    }   }   else   {    if(day > day_30)    {     err_flag = 1;    }    else if(day == day_30)    {     month++;     day = 1;    }    else    {     day++;    }   }   if(month > 12)   {    year++;    month = 1;   }  }  else  {   err_flag = 1;  } } int main() {  time_t now;  char ch, c;  char call_cal[30];  do  {   compute();   if(err_flag)   {    err_flag = 0;    printf("日期输入错误，调用cal命令查询%d年%d月：\n\n",year, month);    sprintf(call_cal, "/usr/bin/cal %d %d",month, year);    system(call_cal);    //system("clear");    while((c=getchar())!='\n' && (c=getchar())!=EOF);    printf("是否重新输入(y/n)：");   }   else   {    printf("第二天为%d-%d-%d。\n",year, month, day);    while((c=getchar())!='\n' && (c=getchar())!=EOF);    printf("是否再次输入日期(y/n)：");   }   ch = getchar();  }  while(ch=='y' || ch=='Y' || ch=='\n');  time(&now);  printf("Now is %s",ctime(&now));  puts("Having a goodday!");  return 0; }