#include <time.h>
#include <malloc.h>
#include <stdio.h>

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

void print_header(FILE* fp,int month,int year)
{
	int index;

	fprintf(fp,"\n");
	fprintf(fp,full_month[month]);
	for(index = 35 - strlen(full_month[month]); index>0; index--)
		fprintf(fp," ");
	fprintf(fp,"%d\n",year);
	for(index = 39; index>0; index--)
		fprintf(fp,"-");


	fprintf(fp,"\nSun   Mon   Tue   Wed   Thu   Fri   Sat");
}

void do_calendar(FILE* fp, int year)
{
	struct tm*		date = (struct tm*) malloc (sizeof(struct tm));
	time_t	seconds;
	int 	month;
	int 	day;
	int		index;

	date->tm_year = year - 1900;
	//Year in tm struct is defined as years since 1900.
	for(month=0; month<12; month++){			//Loop through months 0-11
		date->tm_mon = month;					//Set month in tm struct.
		print_header(fp,date->tm_mon,year);		//Call print header to print month heading
		for(day=1; day<32; day++){				//Loop through days 1-31
			date->tm_mday = day;				//Set day in tm struct

			/*This call is the workhorse.  Once you set the values of the
			  other variables, this call will hash the date to its proper
			  value and fill in the tm struct properly.  The variable seconds
			  is not used for anything but mktime returns a time_t variable
			  and it is proper to capture it.
			*/
			seconds = mktime(date);


			if(day == 1){						//It it is the first day, set proper spacing
				for(index=date->tm_wday;index>0;index--){
					if(index == date->tm_wday)
						fprintf(fp,"\n   ");
					else
						fprintf(fp,"      ");
				}
			}
			if(date->tm_mon != month)			//If tm_mon was changed, that means the day of the month is out of range
				break;							//Drops out of for loop.
			if(date->tm_wday == 0)				//If this is the first day of the week
				fprintf(fp,"\n ");
			else
				fprintf(fp,"    ");
			fprintf(fp,"%2d",day);       		//This left pads single digits
		}
		fprintf(fp,"\n");
	}

}


int main()
{
	int		year;

	printf("Calendar Program\n");
	printf("----------------\n");
	printf("\nEnter year for which to generate calendar: ");
	scanf("%d",&year);
	if(year>=1900)
		printf("Processing for year: %d\n",year);
	else
		printf("Year must be greater than 1900.  Exiting.\n");
		/*Code could be added here to adjust a year that is earlier
		  than 1900 to a like year after 1900.  I don't know how to calc
		  that
		*/
	/*I called do_calendar with the ability to pass a file pointer to file
	  or a port or whatever if desired.
	*/
	do_calendar(stdout,year);

	return 0;
}

#include <string.h>

int do_calendar(FILE* fp, int year)
{
	struct tm*	date;
	time_t		seconds;
	int 		month;
	int 		day;
	int			index;

	time(&seconds);						//Get current time as a long
	date = localtime(&seconds);			//Load tm structure with valid values

	if( (seconds = mktime(date) ) == -1)
				return -1;

	if(do_calendar(stdout,year))
		printf("There was a problem with the mktime function");