c语言关于时间的两个函数

根据日期转换为星期几，以及由天数得到月份，代码如下：

#include<stdio.h>

int datetoweek(int yr, int mn,int day)

{

int i;

int days=0;

int s;

int week;

int mont[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};

if((0==yr%4 && 0!=yr%100)||0==yr%400)

mont[2]=29;

else

mont[2]=28;

for (i=0;i<mn;i++)

days+=mont[i];

days+=day;

s=yr-1+(int)((yr-1)/4)-(int)((yr-1)/100)+(int)((yr-1)/400)+days;

week=s%7;

return week;

}

int main()

{

int week1,week2,week3;

week1 = datetoweek(2015,11,17);

week2 = datetoweek(2015,10,17);

week3 = datetoweek(2015,12,17);

printf("week1=%d,week2=%d,week3=%d \r\n",week1,week2,week3);

return 0;

}

/*

int8 GetMonthFromDays(uint32 days,uint32 year, uint32 *returnDays)

{

int i =0;

uint32 totalday = 0;

for(i =0; i < 12 ; i++) {

if(days < totalday) {

break;

}

if(((year&0x3) == 0)&&(i == 1))

totalday += 29;

else

totalday += norm_month_table[i];

}

if(((year&0x3) == 0)&&(i == 2))

*returnDays = days - totalday + 29 + 1;

else

*returnDays = days - totalday + norm_month_table[i - 1] + 1;

return i;

}

*/

运行结果测试正确，如下图：



运行结果如图：