萬年歷，可查看任何日期對(duì)應(yīng)的星期

注意：下面的程序需要以命令行的格式運(yùn)行，例如，把編繹好的可執(zhí)行文件的名字為 filename，那要查看某2002/01/01就輸入 filename 2002/02/01，要查看2002年1月份就輸入filename 2002/01或filename2002/01/0。
    /*** 萬年歷 ***/
    /*** 命令行:
    若查看某一天,例如 calen 2001/12/28
    若查看某個(gè)月,例如 calen 2001/12/0 或 calen 2001/12
    ***/
    /**************************************************
    1. 以2000/01/01日為星期六為基準(zhǔn)。
    2. dy為該年 1月1號(hào) 到2000年1月1號(hào)的 " 星期差 "
    3. dm為該月以前的月所引起的 " 星期差 "
    4. m2為二月所引起的 " 星期差 "
    **************************************************/
    main(int x,char **date)
    {
    int year=0,month=0,day=0,week;
    int d,i,dm,dy,m2;
    char WEEK[9];
    if (x==1)
    {
    printf ("\n ERROR! you forgot to enter the date you want to view\n");
    exit (0);
    }
    i=0; d=-1;
    while (date[1][i])
    {
    if ((date[1][i]=='/'||date[1][i]=='.')&&d==-1) { d=0; i++; continue; }
    if ((date[1][i]=='/'||date[1][i]=='.')&&d==0) { d=1; i++; continue; }
    if (d==-1) year=year*10+(date[1][i]-'0');
    if (d==0) month=month*10+(date[1][i]-'0');
    if (d==1) day=day*10+(date[1][i]-'0');
    i++;
    }
    if (month<1||month>12)
    { printf ("\n ERROR! the entered MONTH is invalid\n"); exit (0); }
    if (year==2000) { dy=0; m2=1; goto la_100; }
    if (year>2000) d=(year-1-2000)/4-(year-1-2000)/100+(year-1-2000)/400+1;
    else d=(year-2000)/4-(year-2000)/100+(year-2000)/400;
    dy=(year-2000)+d; /*** 該年 1月1號(hào) 到2000年1月1號(hào)的 " 星期差 " ***/
    if((year%4==0&&year%100!=0)||(year%100==0&&year%400==0))
    m2=1; else m2=0; /*** 該年是否潤(rùn) ***/
    la_100: /**** la_100 ****/
    /*** 該月以前的月所引起的 " 星期差 " ***/
    switch (month)
    {
    case 1: dm=0; month=31; break; /*** month 在此存放該月天數(shù) ***/
    case 2: dm=3; month=d==1? 29:28; break;
    case 3: dm=3+m2; month=31; break;
    case 4: dm=6+m2; month=30; break;
    case 5: dm=1+m2; month=31; break;
    case 6: dm=4+m2; month=30; break;
    case 7: dm=6+m2; month=31; break;
    case 8: dm=2+m2; month=31; break;
    case 9: dm=5+m2; month=30; break;
    case 10: dm=m2; month=31; break;
    case 11: dm=3+m2; month=30; break;
    case 12: dm=5+m2; month=31; break;
    }
    if (day<0||day>month)
    { printf ("\n ERROR! the entered DAY is invalid\n"); exit (0); }
    week=(dy+dm+day-1+6)%7; if(week<0) week+=7;
    if (day>0) /*** 判斷查看類型 ***/
    {
    switch (week)
    {
    case 0: strcpy (WEEK,"SUNDAY"); break;
    case 1: strcpy (WEEK,"MONDAY"); break;
    case 2: strcpy (WEEK,"TUESDAY"); break;
    case 3: strcpy (WEEK,"WEDNESDAY"); break;
    case 4: strcpy (WEEK,"THURSDAY"); break;
    case 5: strcpy (WEEK,"FRIDAY"); break;
    case 6: strcpy (WEEK,"SATURDAY"); break;
    }
    printf ("\n this day is %s \( %d \)\n\n OK!\n",WEEK,week);
    }
    else
    {
    week=++week%7;
    printf ("\n the calender of this month as following\n");
    printf ("\n *********************************\n");
    printf (" SUN MON TUE WEN THU FRI STA\n");
    for (i=0;i    for (i=1;i<=month;i++)
    { printf (" %2d ",i); week++; if (week%7==0&&i!=month) printf ("\n"); }
    printf ("\n *********************************\n");
    printf ("\n OK!\n");
    }
    }