定义函数给出任意一天是星期几

输入年月日，输出 星期几。
调用 int YMD_2_WeekDay(int Y, int M, int D)

#include
#include
char *WeekDayName[]={" ","Mon","Tue","Wen","Thu","Fri","Sat","Sun"};
int YMD_2_JD(int Y, int M, int D){
const short MonthDay[]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int JD,i;
JD=D;
for (i=1;iif ((Y%4==0)&&(Y%100!=0)||(Y%400==0) && M>2) JD++;
return JD;
}

int YMD_2_WeekDay(int Y, int M, int D){
int offset,jd,weekD;
offset = ((Y-1)+(Y-1)/4-(Y-1)/100+(Y-1)/400) % 7 ;
jd = YMD_2_JD(Y,M,D);
weekD = (jd + offset) % 7;
return weekD;
}

void main()
{
int y=2011,m=5,d=31;
int dd;
dd = YMD_2_WeekDay(y,m,d);
printf("%4d-%02d-%02d is %s ", y,m,d,WeekDayName[dd] );
}

/*-----------------------------------------------------------------*\
author: wanfustudio
mail : wanfu.liu@163.com
Rights: 任意拷贝，修改，传播包括商业使用
Q & A :
如何疑问，以及想法，不满足的需求
欢迎来函!!!
\*-----------------------------------------------------------------*/

#include
#include
#include
#include

/*这段是注释，放在此处用以说明各个成员的含义，在time.h中定义*/
#if 0
struct tm {
int tm_sec; /* seconds after the minute - [0,59] */
int tm_min; /* minutes after the hour - [0,59] */
int tm_hour; /* hours since midnight - [0,23] */
int tm_mday; /* day of the month - [1,31] */
int tm_mon; /* months since January - [0,11] */
int tm_year; /* years since 1900 */
int tm_wday; /* days since Sunday - [0,6] */
int tm_yday; /* days since January 1 - [0,365] */
int tm_isdst; /* daylight savings time flag */
};
#endif

/*-----------------------------------------------------------------*\
全局变量
\*-----------------------------------------------------------------*/

/* 数组与下面tm结构中定义的tm_wday取值范围相对应 */
const char *Week[]=
{
"星期天",
"星期一",
"星期二",
"星期三",
"星期四",
"星期五",
"星期六"
};

/*-----------------------------------------------------------------*\
函数声明
\*-----------------------------------------------------------------*/

/* 一年中第X天是星期几 */
void GetWeekDay(int year,int num);

/* X年X月X日是一年中的第X天，星期几 */
void GetSomeDay(int year, int mon, int day);

/* X年X月X日再过X天是一年中的第X天，星期几 */
void GetNextTime(int year, int mon, int day,int num);

/* X年某月末日到X年X月某日有多少天 */
int GetDistBetweenTwoDays(int year, int mon, int day, int year2, int mon2, int day2);

/*-----------------------------------------------------------------*\
函数实现
\*-----------------------------------------------------------------*/

void GetSomeDay(int year, int mon, int day)
{
time_t t;//存储需要计算时间距1900的秒数
struct tm test ;//填充这个结构
struct tm *now = NULL;

memset(&test, 0, sizeof(tm));//先清空下

test.tm_year = year - 1900;
test.tm_mon = mon -1;
test.tm_mday = day ;

t = mktime(&test);// 转换成秒
now = localtime(&t);//再转回tm

printf("%d\n", now->tm_yday);//第几天
printf("%s\n", Week[now->tm_wday]);//星期几
}

void GetNextTime(int year, int mon, int day,int num)
{
struct tm *pNext= NULL;
struct tm now, tmp;
time_t t;

memset(&now, 0 , sizeof(struct tm));
memset(&tmp, 0 , sizeof(struct tm));

now.tm_year = year-1900; //指定年
now.tm_mon = mon -1;//指定月份
now.tm_mday = day + num; //指定是哪一天

t = mktime(&now);//转换成秒

pNext = localtime(&t);

printf("%s\n", asctime(pNext));//哪一天
printf("%s\n", Week[pNext->tm_wday]);//星期几

}

void GetWeekDay(int year,int num)
{
time_t t;//存储需要计算时间距1900的秒数
struct tm test ;//填充这个结构
struct tm *now = NULL;

memset(&test, 0, sizeof(tm));//先清空下

test.tm_year = year - 1900;
test.tm_mday = num +1;

t = mktime(&test);// 转换成秒
now = localtime(&t);//再转回tm

printf("%d\n", now->tm_yday);//第几天
printf("%s\n", Week[now->tm_wday]);//星期几
}

int GetDistBetweenTwoDays(int year, int mon, int day, int year2, int mon2, int day2)
{
int distance = 0;
struct tm now, tmp;
time_t t1,t2;
long diff = 0;

memset(&now, 0 , sizeof(struct tm));
memset(&tmp, 0 , sizeof(struct tm));

now.tm_year = year-1900; //指定年
now.tm_mon = mon -1;//指定月份
now.tm_mday = day; //指定是哪一天

tmp.tm_year = year2-1900;
tmp.tm_mon = mon2 -1;
tmp.tm_mday = day2;

t1 = mktime(&now);// 转换成秒
t2 = mktime(&tmp);

diff = (long)fabs(difftime(t1, t2)); /* 算绝对值(秒) */

distance = diff / 3600 / 24; /* 转成天 */

printf("相隔 %d 天\n", distance);

return distance;
}

/*-----------------------------------------------------------------*\
函数测试
\*-----------------------------------------------------------------*/

int main()
{
GetWeekDay(2007,337);
GetSomeDay(2007,12,4);
GetNextTime(2005,12,4,100);
GetDistBetweenTwoDays(2011, 4, 30, 2011, 5, 2);

return 0;
}

/*-----------------------------------------------------------------*\
author: wanfustudio
mail : wanfu.liu@163.com
如何疑问，以及想法，不满足你的需求
欢迎来函!!!
\*-----------------------------------------------------------------*/