main(){ int year,month,day,i=0,n=0; printf(Please input year.month.day\n); loop: scanf(%d.%d.%d,&year,&month,&day); if(month<=0||month>12||day<=0||day>31) { printf(Data error!Please input again.\n); goto loop; } switch(month) { case 1:n=0;break; case 2:n=31;break; case 3:n=59;break; case 4:n=90;break; case 5:n=120;break; case 6:n=151;break; case 7:n=181;break; case 9:n=243;break; case 10:n=273;break; case 11:n=304;break; case 12:n=334; } n+=day; if(year%400==0||(year%4==0&&year%100!=0)) i=1; else i=0; if(i==1&&month>2)n++; printf(It is the %dth day.,n);}参考别人后自己编的,应该是这个吧.输入某月某日计算为一年的第几天.