//转换函数如下，其中通过指针同时向主函数传回月份和天数
void month_day(int year, int yearday, int *month, int *day){
//k月份，leap判断是否闰年（0非闰年1闰年）
int k, leap;
int tab[2][13] = {
{ 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
{ 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
};
leap = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
for (k = 1; yearday>tab[leap][k]; k++){
yearday = yearday - tab[leap][k];
}
*day = yearday;
*month = k;
}输入年份和天数计算出几月几号,布布扣,bubuko.com
输入年份和天数计算出几月几号
原文：http://blog.csdn.net/eh_sky/article/details/25954775
