Calendar

#include <stdio.h>
#include <stdlib.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */


int firstday = 1 ;
int year=0;
int Febuary=0;

char *weekdays[] = {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
char *months[] = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec",};


void prtspace(int first)
{
    int i ;

    for(i=0;i<first%7;i++)
        printf("    ");
}

int firstcal(int y)
{
    int i;
    y = y-1900;
    int flag=0;
    for(i=1;i<=y;i++)
    {
        flag += (!(i%4) && i%100 || !(i%400))? 366 : 365 ;
        //printf("=%d  %d=\n",i,flag%365);
    }
    firstday = (firstday+flag)%7;
    return firstday;

}

void leapjudge(int y)
{
    if(!(y%400) || (y%100) && !(y%4))
    {
        Febuary = 29 ;
        printf("This year %d is leap year\n",y);
    }
    else
    {
        Febuary = 28;
        printf("This year %d is not leap year\n",y);
    }

}

int main(int argc, char *argv[])
{
    int i,j;
    int k;

    int Days[12] = {31,Febuary,31,30,31,30,31,31,30,31,30,31};
    printf("A calender of which year :");
    scanf("%d",&year);

    //閏年二月日數
    leapjudge(year);

    //該年一月的空白日數
    firstcal(year);


    for(i=0;i<12;i++)
    {
        printf("%d\n",Days[i]);
        printf("\t%4s\n",*(months+ i));
        for(k=0;k<7;k++)
        {
            printf("%4s",*(weekdays+ k));

        }
        printf("\n");

        prtspace(firstday);

        for(j=1;j<=Days[i];j++)
        {
            printf(" %3d",j);
            firstday =  (++firstday)%7;
            if(!firstday)
            printf("\n");

        }
        printf("\n");

    }


    system("PAUSE");
    return 0;
}