Program 184:Tell me any Date ,I will tell you the Day

Program 184: Calculate Day from given Date
 

#include <stdio.h>
#include<stdlib.h>
#include <string.h>
char* months[] = {"Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec","Jan","Feb"};
char* days[]= { "sunday","monday", "tuesday", "wednesday", "thursday", "friday", "saturday" };
main()
{
//Using Zellers Rule f = k + [(13*m-1)/5] + D + [D/4] + [C/4] - 2*C
//Ex for 29 Jan 2064
//k---day of the month as 29 
//m-month number as March=1 ..Feb=12,so here it is 11
//D--last two digits of year from above it is 64
//C--first two digits of year from above it is 20
int k,m,D,C,year,i,f,finalday,flag=0;
char str[3];
printf("Enter date \n");
scanf("%d",&k);
if(k<=0||k>31)
{
 printf("Invalid Date\n");
 exit(0);
}

printf("Enter first 3 letters of month of the year ex:-for January enter Jan\n");
scanf("%s",str);


    for(i=0; i<12; i++)
    {
        if(!strcmp(str,months[i]))
        {
            m=i+1;
            flag=1;
            break;
        }
    }
if(flag==0)
{
  printf("Invalid Month\n");
  exit(0);
}

printf("Enter year\n");
scanf("%d",&year);
if(m==11||m==12)
{
 year=year-1;
}
D=year%100;
C=year/100;
    f = (k+(((13*m)-1)/5)+D+(D/4)+(C/4))-(2*C);

if(f>=0)
{
 finalday=f%7;
}
else
{
 finalday=((f%7)+7)%7;
}

   printf("The Day for given %d,%s %d is\n%s\n",k,str,year,days[finalday]);

}

Explanation:

//Coming Soon...

Output: