这个是1984年1月1日是星期日的，你先看看，我再帮你改，最好自己能看懂

#include void main()

{

int year,month,day;

int tempmonth,yearday;

int week,weekday;

unsigned int sum=0;

int tag=0;

printf("输入年、月、日:\n");

scanf("%d %d %d",&year,&month,&day);

tag =( year - 1980 )/4;

sum=(year-1984)*365 + tag;

tempmonth = month - 1;

yearday = 0;

switch(tempmonth)

{

case 12:yearday+=31;

case 11:yearday+=30;

case 10:yearday+=31;

case 9:yearday+=30;

case 8:yearday+=31;

case 7:yearday+=31;

case 6:yearday+=30;

case 5:yearday+=31;

case 4:yearday+=30;

case 3:yearday+=31;

case 2:yearday+=28;

case 1:yearday+=31;

}

yearday = yearday+day;

if ((year-1984)%4==0 && month > 2)

{

yearday+=1;

}

sum=sum+yearday;

if (year==1984)

{

sum-=1;

}

printf("距1984年1月1日一共有%d天\n",sum);

/*上面是计算输入的日期距1984年1月1日一共经历了多少天*/

weekday = (sum-1) % 7;

week = yearday / 7;

printf("今天是第%d个星期，星期%d",week,weekday);

return ;

}

下面是修改好的，能多给些分嘛？写程序不容易，还有，好好学习，这些不难，就是多花点时间而已

#include void main()

{

int year,month,day;

int tempmonth,yearday;

int week,weekday;

int sum=0;

int tag=0;

printf("输入年、月、日:\n");

scanf("%d %d %d",&year,&month,&day);

tag =( year - 1988 )/4;

printf("tag=%d\n",tag);

sum=(year-1990)*365 + tag;

tempmonth = month - 1;

yearday = 0;

switch(tempmonth)

{

case 12:yearday+=31;

case 11:yearday+=30;

case 10:yearday+=31;

case 9:yearday+=30;

case 8:yearday+=31;

case 7:yearday+=31;

case 6:yearday+=30;

case 5:yearday+=31;

case 4:yearday+=30;

case 3:yearday+=31;

case 2:yearday+=28;

case 1:yearday+=31;

}

yearday = yearday+day;

if ((year-1988)%4==0 && month > 2)

{

yearday+=1;

}

sum=sum+yearday;

printf("sum=%d\n",sum);

printf("距1990年1月1日一共有%d天\n",sum);

/*上面是计算输入的日期距1990年1月1日一共经历了多少天*/

weekday = (sum-1) % 7+1;

week = yearday / 7;

printf("今天是第%d个星期，星期%d",week,weekday);

return ;

}