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Find Weekday using Zeller's Algorithm
Zeller’s Algorithm is used to find the weekday from a given date. The formula to find weekday using Zeller’s Algorithm is here:
The formula is containing some variables; They are −
d − The day of the date.
m: It is the month code. From March to December it is 3 to 12, for January it is 13, and for February it is 14. When we consider January or February, then given year will be decreased by 1.
y − Last two digits of the year
c − first two digits of the year
w − The weekday. When it is 0, it is Saturday, when it is 6, it means Friday
Input and Output
Input: The day, month and the year: 4, 1, 1997 Output: It was: Saturday
Algorithm
zellersAlgorithm(day, month, year)
Input: The date of the day.
Output: Which day it was, (Sunday to Saturday).
Begin if month > 2, then mon := month else mon := 12 + month decrease year by 1 y := last two digit of the year c := first two digit of the year w := day + floor((13*(mon+1))/5) + y + floor(y/4) + floor(c/4) + 5*c w := w mod 7 return weekday[w] //weekday will hold days from Saturday to Friday End
Example
#include<iostream>
#include<cmath>
using namespace std;
string weekday[7] = {"Saturday","Sunday","Monday","Tuesday","Wednesday","Thursday","Friday"};
string zellersAlgorithm(int day, int month, int year) {
int mon;
if(month > 2)
mon = month; //for march to december month code is same as month
else {
mon = (12+month); //for Jan and Feb, month code will be 13 and 14
year--; //decrease year for month Jan and Feb
}
int y = year % 100; //last two digit
int c = year / 100; //first two digit
int w = (day + floor((13*(mon+1))/5) + y + floor(y/4) + floor(c/4) + (5*c));
w = w % 7;
return weekday[w];
}
int main() {
int day, month, year;
cout << "Enter Day: "; cin >>day;
cout << "Enter Month: "; cin >>month;
cout << "Enter Year: "; cin >>year;
cout << "It was: " <<zellersAlgorithm(day, month, year);
}Output
Enter Day: 04 Enter Month: 01 Enter Year: 1997 It was: Saturday
Updated on: 17-Jun-2020
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