Thread: Calendar program that calculates a given day on a given date

Hi,

Though an easy one I made this program with my own logic.The program determines what day it is on a particular date For ex- Thursday on 12 july 2012.

I tested it and gave the correct output. Hope it gives the correct output always

Code:

#include<stdio.h>
#include<conio.h>

/*Function to calculate whether the entered date is correct or not*/
 
int correct_date_calc(int day, int month, int year)
{
const int ref_year=2012;
int lp_yr_flg=0;
 
 if(year<=2012)
 {
  if(((ref_year - year)%4) == 0)
  {
   lp_yr_flg=1;
  }
 }
 
 else if(year>2012)
 {
  if(((year - ref_year)%4) == 0)
  {
   lp_yr_flg=1;
  }
 }
 
 if(month>12 || month<1)
 {
  return 0;
 }
 
 if((lp_yr_flg==1) && (month==2) && (day>29))
 {
  return 0;
 }
 
 else if((lp_yr_flg==0) && (month==2) && (day>28))
 {
  return 0;
 }
 
 else if(((month == 1) || (month == 3) || (month == 5) || (month == 7) || (month == 8) || (month == 10) || (month == 12)) && (day>31 || day<1))
 {
  return 0;
 }
 
 else if(((month == 4) || (month == 6) || (month == 9) || (month ==11)) && (day>30 || day<1))
 {
  return 0;
 }
 
 return 1;
}
 

/*Function to Calculate leap year*/
 
int leap_year_calc(int year_lp)
{
const int ref_year=2012;
int lp_yr_flg=0;
 
 if(year_lp<=2012)
 {
  if(((ref_year - year_lp)%4) == 0)
  {
   lp_yr_flg=1;
   return lp_yr_flg;
  }
 }
 
 else if(year_lp>2012)
 {
  if(((year_lp - ref_year)%4) == 0)
  {
   lp_yr_flg=1;
   return lp_yr_flg;
  }
 }
 
 return 0;
}
 

/*Fucntion to Calculate the given days in a month*/
 
int no_of_days(int month, int year)
{
int day=0;
int leap_yr = 0;
 
 leap_yr = leap_year_calc(year);
 if((month == 1) || (month == 3) || (month == 5) || (month == 7) || (month == 8) || (month == 10) || (month == 12))
 {
  day=31;
  return day;
 }
 
 else if((month == 4) || (month == 6) || (month == 9) || (month ==11))
 {
  day=30;
  return day;
 }
 
 else if((month == 2) && (leap_yr == 1))
 {
  day=29;
  return day;
 }
 
 else if((month == 2) && (leap_yr == 0))
 {
  day=28;
  return day;
 }
}
 

/*Function to calculate the day before the reference date. Here it is 31/12/2012.*/
 
int bef_ref_date(int day_bef,int month_bef,int year_bef)
{
 
int day_dec,year_dec,month_dec=12,day=1;
 for(year_dec=2012; year_dec>=year_bef; year_dec--)
 {
  for(month_dec=12; month_dec>=1; month_dec--)
  {
   for(day_dec=no_of_days(month_dec, year_dec); day_dec>=1; day_dec--)
   {
    if(year_dec==year_bef && month_dec==month_bef && day_dec==day_bef)
    {
     return day;
    }
 
    day--;
    if(day==0)
    {
    day=7;
    }
   }
  }
 }
}
 
 

/*Function to calculate the day after the reference date. Here it is 1/1/2012.*/
 
int aft_ref_date(int day_aft,int month_aft,int year_aft)
{
 
int day_inc, year_inc, month_inc=1, day=1, month_day_lim;
 for(year_inc=2012; year_inc<=year_aft; year_inc++)
 {
  for(month_inc=1; month_inc<=12; month_inc++)
  {
   month_day_lim = no_of_days(month_inc, year_inc);
 
   for(day_inc=1; day_inc<=month_day_lim; day_inc++)
   {
    if(year_inc==year_aft && month_inc==month_aft && day_inc==day_aft)
    {
     return day;
    }
 
    day++;
    if(day==8)
    {
    day=1;
    }
   }
  }
 }
}
 

void main()
{
int day, month, year, day_date, crct_date_flg=0;
const int ref_year = 2012;
 
 printf("Enter the Day ");
 scanf("%d",&day);
 
 printf("\nEnter the Month ");
 scanf("%d",&month);
 
 printf("\nEnter the year ");
 scanf("%d",&year);
 
 crct_date_flg = correct_date_calc(day, month, year);
 clrscr();
 if(crct_date_flg == 0)
 {
  printf("Date Entered is an Invalid Date!!");
  getch();
 }
 
 clrscr();
if(crct_date_flg==1)
{
 if(year <= ref_year)
 {
  day_date = bef_ref_date(day, month, year);
 
  switch (day_date)
  {
   case 1:
    printf("The day was Monday");
    break;
   case 2:
    printf("The day was Tuesday");
    break;
   case 3:
    printf("The day was Wednesday");
    break;
   case 4:
    printf("The day was Thursday");
    break;
   case 5:
    printf("The day was Friday");
    break;
   case 6:
    printf("The day was Saturday");
    break;
   case 7:
    printf("The day was Sunday");
    break;
  }
 }
 
 else if (year > ref_year)
 {
  day_date = aft_ref_date(day, month, year);
 
  switch (day_date)
  {
   case 1:
    printf("The day is Sunday");
    break;
   case 2:
    printf("The day is Monday");
    break;
   case 3:
    printf("The day is Tuesday");
    break;
   case 4:
    printf("The day is Wednesday");
    break;
   case 5:
    printf("The day is Thursday");
    break;
   case 6:
    printf("The day is Friday");
    break;
   case 7:
    printf("The day is Saturday");
    break;
  }
 }
 
getch();
clrscr();
}
}

I'm assuming there's no question associated with this post?

Well, it gave the right day for my birthday in four years - after eliminating the non-standard header "conio.h" and all associated (and not-required) "getch()" and "clrscr()" calls.

Just a few nit-picks:
- "void main()" should be "int main(void)" ... and you should "return 0" at the end of the main function
- All your functions are defined to return an integer value, though most of them don't - though it was difficult to tell at first glance because;
- The indentation in this program (one space!?) made it difficult to scan easily by eye

However, the value of this program lies in what you've learned. If you've learned a good deal, and got some more experience, then you're doing well. My criticisms are intended to be helpful, and hope they're taken in that spirit.