long int f(int year,int month)
{/*f(年，月)＝年－1，如月<3;否則，f(年，月)＝年*/
if(month<3) return year-1;
else return year;
}
long int g(int month)
{/*g(月)＝月＋13，如月<3;否則，g(月)＝月＋1*/
if(month<3) return month+13;
else return month+1;
}
long int n(int year,int month,int day)
{
/*N=1461*f(年、月)/4+153*g(月)/5+日*/
return 1461L*f(year,month)/4+153L*g(month)/5+day;
}
int w(int year,int month,int day)
{
/*w=(N-621049)%7(0<=w<7)*/
return(int)((n(year,month,day)%7-621049L%7+7)%7);
}
int date[12][6][7];
int day_tbl[ ][12]={{31,28,31,30,31,30,31,31,30,31,30,31},
{31,29,31,30,31,30,31,31,30,31,30,31}};
main()
{int sw,leap,i,j,k,wd,day;
int year;/*年*/
char title[]="SUN MON TUE WED THU FRI SAT";
clrscr();
printf("Please input the year whose calendar you want to know: ");/*輸入年*/
scanf("%d%*c",&year);/*輸入年份值和掠過值後的回車*/
sw=w(year,1,1);
leap=year%4==0&&year%100||year%400==0;/*判閏年*/
for(i=0;i<12;i++)
for(j=0;j<6;j++)
for(k=0;k<7;k++)
date[i][j][k]=0;/*日期表置0*/
for(i=0;i<12;i++)/*壹年十二個月*/
for(wd=0,day=1;day<=day_tbl[leap][i];day++)
{/*將第i＋1月的日期填入日期表*/
date[i][wd][sw]=day;
sw=++sw%7;/*每星期七天，以0至6計數*/
if(sw==0) wd++;/*日期表每七天壹行，星期天開始新的壹行*/
}
printf("\n|==================The Calendar of Year %d =====================|\n|",year);
for(i=0;i<6;i++)
{/*先測算第i+1月和第i+7月的最大星期數*/
for(wd=0,k=0;k<7;k++)/*日期表的第六行有日期，則wd!=0*/
wd+=date[i][5][k]+date[i+6][5][k];
wd=wd?6:5;
printf("%2d %s %2d %s |\n|",i+1,title,i+7,title);
for(j=0;j<wd;j++)
{
printf(" ");/*輸出四個空白符*/
/*左欄為第i+1月，右欄為第i+7月*/
for(k=0;k<7;k++)
if(date[i][j][k])
printf("%4d",date[i][j][k]);
else printf(" ");
printf(" ");/*輸出十個空白符*/
for(k=0;k<7;k++)
if(date[i+6][j][k])
printf("%4d",date[i+6][j][k]);
else printf(" ");
printf(" |\n|");
}
/*scanf("%*c");/*鍵入回車輸出下壹個月的日歷*/
}
puts("=================================================================|");
puts("\n Press any key to quit...");
getch();
}