新世纪万年历

#include<stdio.h>
#define Mon   1
#define Tues  2
#define Wed   3
#define Thur  4
#define Fri   5
#define Sat   6
#define Sun   0

#define January_days   31
#define February_days   28
#define March_days    31
#define April_days    30
#define May_days     31
#define June_days     30
#define July_days     31
#define August_days    31
#define September_days  30
#define October_days   31
#define November_days   30
#define December_days   31

#define first1month January_days
#define first2month January_days+February_days
#define first3month January_days+February_days+March_days
#define first4month January_days+February_days+March_days+April_days
#define first5month January_days+February_days+March_days+April_days+May_days
#define first6month January_days+February_days+March_days+April_days+May_days+June_days
#define first7month January_days+February_days+March_days+April_days+May_days+June_days \
             +July_days
#define first8month January_days+February_days+March_days+April_days+May_days+June_days \
             +July_days+August_days
#define first9month January_days+February_days+March_days+April_days+May_days+June_days \
             +July_days+August_days+September_days
#define first10month January_days+February_days+March_days+April_days+May_days+June_days \
             +July_days+August_days+September_days+October_days
#define first11month January_days+February_days+March_days+April_days+May_days+June_days \
             +July_days+August_days+September_days+October_days+November_days

int known_weekday = Tues;
int known_year = 1901;
int konwn_month = 1;
int known_day = 1;


int day_count(int month)
{
    switch(month)
    {
    case 1:
        return 0;
        break;
    case 2:
        return first1month;
        break;
    case 3:
        return first2month;
        break;
    case 4:
        return first3month;
        break;
    case 5:
        return first4month;
        break;
    case 6:
        return first5month;
        break;
    case 7:
        return first6month;
        break;
    case 8:
        return first7month;
        break;
    case 9:
        return first8month;
        break;
    case 10:
        return first9month;
        break;
    case 11:
        return first10month;
        break;
    case 12:
        return first11month;
        break;
    }
}


char * month_name(int month)
{
    switch(month)
    {
    case 1:
        return "一月";
        break;
    case 2:
        return "二月";
        break;
    case 3:
        return "三月";
        break;
    case 4:
        return "四月";
        break;
    case 5:
        return "五月";
        break;
    case 6:
        return "六月";
        break;
    case 7:
        return "七月";
        break;
    case 8:
        return "八月";
        break;
    case 9:
        return "九月";
        break;
    case 10:
        return "十月";
        break;
    case 11:
        return "十一月";
        break;
    case 12:
        return "十二月";
        break;
    default:
        break;
    }
}
///按格式打印某年某月名称
void first_line_print(int month, int year)
{
    printf("%8d年 %s \n",year, month_name(month));
}

///按格式打印星期名称
void week_print()
{
    printf("%-3s%-3s%-3s%-3s%-3s%-3s%-3s\n","Su", "Mo", "Tu", "We", "Th", "Fr", "Sa");
}

///计算该年该月份与已知日子之间的距离天数
int date_distance_count(int month, int year)
{
    int leap_year_count=0,i,distance;
    if(year>known_year)
    {
        ///判断输入年份之前的闰年
        for (i=known_year; i<year; i++)
        {
            if( ( (i%4==0)&&(i%100!=0) )||(i%400==0))
            {
                leap_year_count++;
            }
        }
        ///判断输入年份是否为闰年
        if(month>2)
        {
            if( ( (year%4==0)&&(year%100)!=0 ) || (year%400==0) )
            {
                leap_year_count++;
            }
        }

    }
    else
    {
        if (year == known_year)
        {
            if (month > 2)
            {
                leap_year_count = 0;
            }
        }
    }


    distance = (year - known_year)*365 + leap_year_count + day_count(month);
    return distance;

}

///确定该月份第一天是星期几
int makesure_firstday_weekday(int month, int year)
{
    int date_distance = 0;
    int weekday;

    date_distance=date_distance_count(month,year);

    weekday=(date_distance+known_weekday)%7;

    return weekday;

}

///依次打印出该月份的日子
void print_in_turn(int month, int firstday, int year)
{
    int i;
    int weekday;

    switch(firstday)
    {
    case Sun:
        break;
    case Mon:
        printf("%-3s","");
        break;
    case Tues:
        printf("%-6s","");
        break;
    case Wed:
        printf("%-9s","");
        break;
    case Thur:
        printf("%-12s","");
        break;
    case Fri:
        printf("%-15s","");
        break;
    case Sat:
        printf("%-18s","");
        break;
    }

    switch(month)
    {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
    {
        for(i=0; i<31; i++)
        {
            weekday = (firstday + i)%7;
            printf("%-3d",i+1);

            if(weekday == Sat)
            {
                printf("\n");
            }
        }
        break;
    }
    case 2:
    {
        if(((year%4 == 0) && (year%100 != 0) ) || (year%400 == 0))
        {
            for(i=0; i<29; i++)
            {
                weekday = (firstday + i)%7;
                printf("%-3d",i+1);

                if(weekday == Sat)
                {
                    printf("\n");
                }
            }
            break;
        }
        else
        {
            for(i=0; i<28; i++)
            {
                weekday = (firstday + i)%7;
                printf("%-3d",i+1);

                if(weekday == Sat)
                {
                    printf("\n");
                }
            }
            break;
        }

    }
    case 4:
    case 6:
    case 9:
    case 11:
    {
        for(i=0; i<30; i++)
        {
            weekday = (firstday + i)%7;
            printf("%-3d",i+1);

            if(weekday == Sat)
            {
                printf("\n");
            }
        }
        break;
    }
    }


}


///日期输出
void date_print(int month, int year)
{
    int firstday;
    firstday=makesure_firstday_weekday(month, year);
    print_in_turn(month,firstday,year);
    printf("\n");
}


///月份的输出
void main_month(int month,int year)
{
    first_line_print(month, year);
    week_print();
    date_print(month, year);
    printf("\n\n");
}


///打印日历
void main_calendar(int year)
{
    int i;
    for(i=1; i<=12; i++)
    {
        main_month(i,year);
    }
}


///主函数
int main()
{
    int year;
    printf("请输入年份：year = ");
    scanf("%d",&year);
    if(year<1901)
    {
        printf("请重新输入年份:\n");
        scanf("%d",&year);

    }
    main_calendar(year);
    return 0;



}

引入先人的宏定义缩减了代码时间 哈哈哈