Question

Use Zeller’s algorithm to figure out the days of the week for a given date in c.

W = (d + 13(m+1)/5 + y + y/4 + c/4 - 2c + 6) mod 7

Y is the year minus 1 for January or February, and the year for any other month

y is the last 2 digits of Y

c is the first 2 digits of Y

d is the day of the month (1 to 31)

m is the shifted month (March=3,...January = 13, February=14)

w is the day of week (0=Sunday,..,6=Saturday)

Output should look the following:

Please enter the day [YYYY/Month/Day]: 2020/1/1

Wednesday

Answer 1

I have written the program using C PROGRAMMING LANGUAGE.

INPUT:

I have given the Input date as 24/09/2019 (DD/MM/YYYY)

OUTPUT :

CODE :

//included the stdio library

#include <stdio.h>

//function definition for getFirstDayOfMonth

int getFirstDayOfMonth(int mon, int year) {

//Zeller's algorithm

int Adjustedmonth,Adjustedyear,day,century,output;

//declare adjusted month, set to (mon + 9) % 12 + 1

Adjustedmonth = (mon + 9) % 12 + 1;

//declare adjusted year, set to year - 2000

Adjustedyear = year - 2000;

/*if adjusted month is greater than 10:

subtract one from adjusted year*/

if(Adjustedmonth > 10){

Adjustedyear = Adjustedyear - 1;

}

//declare day, set to 1

day = 24;

//declare century, set to 20

century = 20;

/*declare output, set to (13 * adjusted mon - 1) / 5 + adjusted year / 4 + century / 4 + day + adjusted year - 2 * century;*/

output = (13 * Adjustedmonth - 1) / 5 + Adjustedyear / 4 + century / 4 + day + Adjustedyear - 2 * century;

// mod output by 7

output = output%7;

//add 7 to output

output = output + 7;

//mod output by 7 again

output = (output+1)%7;

return output; //returned the output

}

//main method

int main(void) {

int result ;//declared the result integer variable

//Calling the getFirstDayOfMonth function

result = getFirstDayOfMonth(9,2019);

printf("\nOUTPUT : \n");//print statement

//Switch Case

switch (result)

{

case 0 : printf("Saturday \n"); break;

case 1 : printf("Sunday \n"); break;

case 2 : printf("Monday \n"); break;

case 3 : printf("Tuesday \n"); break;

case 4 : printf("Wednesday \n"); break;

case 5 : printf("Thursday \n"); break;

case 6 : printf("Friday \n"); break;

}

return 0;//returned 0

}

Thanks..