Create a program should use Zeller's rule to output the day of the week any date occurred and for each weekday, output a proverb, fortune, piece of wisdom, etc.

Question

I am creating a Zeller's program but not sure how to. Please help me out.

Research a rule called "Zeller's Congruence". This rule provides a complex formula that can be used to determine what day of the week any particular date occurred. For example, if the user entered September 4, 1984, the program would output Tuesday.  

Your program should use Zeller's rule to output the day of the week any date occurred and for each weekday, output a proverb, fortune, piece of wisdom, etc...

For example, September 4, 1984, was a Tuesday. "Tuesday's child is full of grace."

Answer 1

Lets start by writing the Gregorian Zeller's Congruence formula (official form) that determines what day it is based on the date entered:

h = (q + (13(m+1)/5) + K + (K/4) + (J/4) - 2J) mod 7

where:

1. q - day of month
2. m - month (Ex. march = 3, january = 13, etc)
3. K - year of the century = year % 100
4. J = century = year/100

Note that if the month is lets say January, use 13 and subtract 1 from year or if the month is february, use 14 and subtract 1 from year.

Moreover, the formula should output a number from 0 to 6 where 0 represents Saturday, 1 represents Sunday, 2 represents Monday and so forth...

Lets implement this program using C++ as our programming language:

#include <iostream>

#include <string>

using namespace std;

// Returns day of week using Gregorian Zeller's formula

// 0=Sat, 1=Sun, 2=Mon, 3=Tue, 4=Wed, 5=Thu, 6=Fri

int zeller_congruence(int year, int month, int day) {

int q = day;

int m = month;

int Y = year;

// Adjust Jan and Feb to months 13 and 14 of previous year

if (month == 1) {

m = 13;

Y--;

} else if (month == 2) {

m = 14;

Y--;

}

int K = Y % 100; // year of century

int J = Y / 100; // century

// implementing Zeller's formula

int h = (q + (13 * (m + 1)) / 5 + K + K / 4 + J / 4 - 2 * J) % 7;

if (h < 0)

h += 7; // fixes negative result

return h;

}

int main() {

int year, month, day;

// Get date from user

cout << "Enter date (year month day): ";

cin >> year >> month >> day;

// Weekday names

string weekday[7] = {

"Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday"

};

// Proverbs for each weekday

string proverb[7] = {

"Saturday: Rest and renew.",

"Sunday: Begin with gratitude.",

"Monday: Fresh start, fresh focus.",

"Tuesday: Consistency today creates success tomorrow.",

"Wednesday: Keep going, you're halfway.",

"Thursday: Persistence builds success.",

"Friday: Finish strong."

};

// Calculate weekday

int h = zeller_congruence(year, month, day);

// Display result

cout << "That day was a " << weekday[h] << endl;

cout << proverb[h] << endl;

return 0;

}

Comments are provided in the code to state what each part of the code is doing. So, if you input for example 1984 9 4, it outputs:

That day was a Tuesday

Tuesday: Consistency today creates success tomorrow.

Answer 2

As a computer scientist, your task is to turn mathematical ideas into functional code so that the computer can solve a problem conveniently for humans. In this case, you need to look up the mathematical idea of Zeller's Congruence, which is a mathematical formula that takes the number representation of the month, the day of the month, and the year and calculates the day of the week, and convert it into code for your chosen programming language. Your program has to ask the user for the date and from the user's input it needs to get the month, day, and year as numbers to put into the mathematical formula that you have translated into computer code. Once the day of the week is calculated as a number using Zeller's Congruence, your program needs to take that number and display the name for that day of the week. In addition, your program needs to have a particular piece of information unique to each day of the week to display based on the day of the week that is calculated. If you are familiar with arrays, you could have one array for the names of the days of the week and one array for the unique pieces of information, and then use the number of the day of the week that is computed by the Zeller's Congruence formula as the index into those arrays to retrieve the appropriate information for your program to output.