Calendar Program

This program prints Weekdays of specified date. It even prints calendar of a given year too.

/*Ccalendar library*/
#include<stdio.h>
#include<string.h>
#include<conio.h>
int getNumberOfDays(int month,int year)
{
switch(month)
{
case 1 : return(31);
case 2 : if(year%4==0)
return(29);
else
return(28);
case 3 : return(31);
case 4 : return(30);
case 5 : return(31);
case 6 : return(30);
case 7 : return(31);
case 8 : return(31);
case 9 : return(30);
case 10: return(31);
case 11: return(30);
case 12: return(31);
default: return(-1);
}
}
char *getName(int odd)
{
switch(odd)
{
case 0 :return("Sunday");
case 1 :return("Monday");
case 2 :return("Tuesday");
case 3 :return("Wednesday");
case 4 :return("Thursday");
case 5 :return("Friday");
case 6 :return("Saturday");
default:return("Error in getName() module.Invalid argument
passed");
}
}
int getOddNumber(int day,int mon,int year)
{
int res=0,t1,t2,y=year;
year = year-1600;
while(year>=100)
{
res=res+5;
year=year-100;
}
res=(res%7);
t1=((year-1)/4);
t2=(year-1)-t1;
t1=(t1*2)+t2;
t1=(t1%7);
res = res+t1;
res=res%7;
t2=0;
for(t1=1;t1<mon;t1++)
{
t2+=getNumberOfDays(t1,y);
}
t2 = t2+day;
t2 = t2%7;
res = res+t2;
res = res%7;
if(y>2000)
res=res+1;
res = res%7;
return res;
}
char *getWeek(int dd,int mm,int yy)
{
int odd;
if(!(mm>=1 && mm<=12))
{
return("Invalid month value");
}
if(!(dd>=1 && dd<=getNumberOfDays(mm,yy)))
{
return("Invalid date");
}
if(yy>=1600)
{
odd = getOddNumber(dd,mm,yy);
odd=odd%7;
return(getName(odd));
}
else
{
return("
Please give year more than 1600");
}
}
void printMonth(int mon,int year,int x,int y)
{
int nod,odd,cnt,d=1,x1=x,y1=y;
if(!(mon>=1 && mon<=12))
{
printf("
INVALID MONTH");
getch();
return;
}
if(!(year>=1600))
{
printf("
INVALID YEAR");
getch();
return;
}
if(x<=0)
x=wherex();
if(y<=0)
y=wherey();
gotoxy(x,y);
textcolor(RED);
cprintf("S");
textcolor(YELLOW);
cprintf(" M T W T F S");
/* 1234567891234567891234567 */
textcolor(7);
cprintf("");
y++;
nod=getNumberOfDays(mon,year);
odd=getOddNumber(d,mon,year);
switch(odd)
{
case 0 : x=x;
cnt=1;
break;
case 1 : x=x+4;
cnt=2;
break;
case 2 : x=x+8;
cnt=3;
break;
case 3 : x=x+12;
cnt=4;
break;
case 4 : x=x+16;
cnt=5;
break;
case 5 : x=x+20;
cnt=6;
break;
case 6 : x=x+24;
cnt=7;
break;
default : printf("

INVALID DATA FROM THE getOddNumber()
MODULE");
return;
}
gotoxy(25,25);
gotoxy(x,y);
printf("%02d",d);
for(d=2;d<=nod;d++)
{
if(cnt%7==0)
{
y++;
cnt=0;
x=x1-4;
}
x = x+4;
cnt++;
gotoxy(x,y);
printf("%02d",d);
}
}
main()
{
char ch='k';
int dd,mm,yy;
while(ch!='0')
{
clrscr();
printf("




1.Know the day");
printf("
2.Print the month");
printf("
0.EXIT");
printf("

ENTER YOUR CHOICE : ");
flushall();
fflush(stdin);
ch=getche();
clrscr();
switch(ch)
{
case '1': printf("Enter date (DD MM YYYY) : ");
scanf("%d %d %d",&dd,&mm,&yy);
printf("
Day is : %s",getWeek(dd,mm,yy));
flushall();
getch();
break;
case '2' : printf("Enter month and year (MM YYYY) : ");
scanf("%d %d",&mm,&yy);
printf("

");
printMonth(mm,yy,-1,-1);
flushall();
getch();
break;
case '0' : exit(0);
}
}
}