Question

In C programming. How do you build a calendar? I can't get the days to work right.

This is what I have so far

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

int dow(int year, int month, int day)
{
    static int t[] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
    year -= month < 3;
    return (year + year/4 - year/100 + year/400 + t[month-1] + day) % 7;
}

int main()
{

    int year, month, day,daysM;

    printf("Please input the year: ");
    scanf("%d",&year);

    char *months[]={"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

    int monthDay[]={31,28,31,30,31,30,31,31,30,31,30,31};

    if (year==-1){
        printf("Error, no year specified\n");
        return 1;
    }
    if (year < 1752) {
        printf("Error, year is earlier than 1752\n");
        return 1;
    }

    if ((year + year/4 - year/100 + year/400 + day) % 7)
    {
        monthDay[1]=29;
    }

    for (month=0; month<12; month++)
    {
        daysM=monthDay[month];
        printf("\n%s        %d\n",months[month],year);
        printf(" Sun Mon Tue Wed Thu Fri Sat\n\n");

        for(day=1;day<daysM;day++)
        {
            printf("%5d",day);
            if (day>6)
            {
                printf("\n");
            }

        }
    }

}

Answer 1

Check this program in C it will work fine for the calendar to work

/*This program prints a calendar for a year specified. The user enters a
     year for the calendar and the programs automatically prints the calendar
     in text format.
     The codes are: day_code (0 = Sun, 1 = Mon, etc.)
                    leap_year (0 = no leap year, 1 = leap year)   */
#include <stdio.h>
#include <stdlib.h>       
#define TRUE 1
#define FALSE 0
int get_day_code (int year);
int get_leap_year (int year);
void print_calendar (FILE *fout, int year, int day_code, int leap_year);
int get_year (void);
main()
{
   
   int year, day_code, leap_year; 
   
   FILE *fout;
   
   fout = fopen ("calendar.txt", "w");
   
   year = get_year();                           
   
   day_code = get_day_code (year);
   
   leap_year = get_leap_year (year);
   
   print_calendar(fout, year, day_code, leap_year);
   
   printf("Open up \'calendar.txt\' to see your calendar...\n");
   
   system("pause");
     
}
     
int get_year (void)
{
int year;
printf ("Enter a year: ");
scanf ("%d", &year);
return year;
}             
int get_day_code (int year)
{
int day_code;
int x1, x2, x3;
        x1 = (year - 1.)/ 4.0;
        x2 = (year - 1.)/ 100.;
        x3 = (year - 1.)/ 400.;
day_code = (year + x1 - x2 + x3) %7;
return day_code;
}             
int get_leap_year (int year)
{
        
//if((year% 4) == 0 );
if(year% 4==0 && year%100 != 0 || year%400==0)
   return TRUE;
   else return FALSE;   
                
}
void print_calendar (FILE *fout, int year, int day_code, int leap_year) //function header
{
        int  days_in_month,     /* number of days in month currently 
                                                     being printed */
         day,       /* counter for day of month */
         month;     /* month = 1 is Jan, month = 2 is Feb, etc. */
     fprintf (fout,"                   %d", year);
     for ( month = 1; month <= 12; month++ ) {
          switch ( month ) { /* print name and set days_in_month */
          case 1:
               fprintf(fout,"\n\nJanuary" );
               days_in_month = 31;
               break;
          case 2:
               fprintf(fout,"\n\nFebruary" );
               days_in_month = leap_year ? 29 : 28;
               break;
          case 3:
               fprintf(fout, "\n\nMarch" );
               days_in_month = 31;
               break;
          case 4:
               fprintf(fout,"\n\nApril" );
               days_in_month = 30;
               break;
          case 5:
               fprintf(fout,"\n\nMay" );
               days_in_month = 31;
               break;
          case 6:
               fprintf(fout,"\n\nJune" );
               days_in_month = 30;
               break;
          case 7:
               fprintf(fout,"\n\nJuly" );
               days_in_month = 31;
               break;
          case 8:
               fprintf(fout,"\n\nAugust" );
               days_in_month = 31;
               break;
          case 9:
               fprintf(fout,"\n\nSeptember" );
               days_in_month = 30;
               break;
          case 10:
               fprintf(fout,"\n\nOctober" );
               days_in_month = 31;
               break;
          case 11:
               fprintf(fout,"\n\nNovember" );
               days_in_month = 30;
               break;
          case 12:
               fprintf(fout,"\n\nDecember" );
               days_in_month = 31;
               break;
          }
          fprintf(fout,"\n\nSun  Mon  Tue  Wed  Thu  Fri  Sat\n" );
          /* advance printer to correct position for first date */
          for ( day = 1; day <= 1 + day_code * 5; day++ )
               fprintf(fout," " );
          /* print the dates for one month */
          for ( day = 1; day <= days_in_month; day++ ) {
               fprintf(fout,"%2d", day );
               if ( ( day + day_code ) % 7 > 0 ) /* before Sat? */
                    /* move to next day in same week */
                    fprintf(fout,"   " );
               else  /* skip to next line to start with Sun */
                    fprintf(fout, "\n " );
          }
          /* set day_code for next month to begin */
          day_code = ( day_code + days_in_month ) % 7;
     }
}