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Find day of the week for a given date

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Write a function that calculates the day of the week for any particular date in the past or future. A typical application is to calculate the day of the week on which someone was born or some other special event occurred. 

Recommended Practice

Following is a simple function suggested by Sakamoto, Lachman, Keith and Craver to calculate day. The following function returns 0 for Sunday, 1 for Monday, etc.

Understanding the Maths:

14/09/1998
dd=14
mm=09
yyyy=1998 //non-leap year

Step 1: Information to be remembered.
 Magic Number Month array.
 For Year: {0,3,3,6,1,4,6,2,5,0,3,5}
 DAY array starting from 0-6: {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}
 Century Year Value: 1600-1699 = 6
      1700-1799 = 4
      1800-1899 = 2
      1900-1999 = 0
      2000-2099 = 6..

Step 2: Calculations as per the steps
 
 Last 2 digits of the year:  98
 Divide the above by 4:     24
 Take the date(dd):      14
 Take month value from array: 5 (for September month number 9)
 Take century year value:  0  ( 1998 is in the range 1900-1999 thus 0)
          -----
 Sum:        141
 
 Divide the Sum by 7 and get the remainder: 141 % 7 = 1
 
 Check the Day array starting from index 0: Day[1] = Monday

**If leap year it will be the remainder-1

C++




/* A program to find day of a given date */
#include <bits/stdc++.h>
using namespace std;
 
int dayofweek(int d, int m, int y)
{
    static int t[] = { 0, 3, 2, 5, 0, 3,
                       5, 1, 4, 6, 2, 4 };
    y -= m < 3;
    return ( y + y / 4 - y / 100 +
             y / 400 + t[m - 1] + d) % 7;
}
 
// Driver Code
int main()
{
    int day = dayofweek(30, 8, 2010);
    cout << day;
 
    return 0;
}
 
// This is code is contributed
// by rathbhupendra


C




// C code to find day of a given date
#include <stdio.h>
 
int dayofweek(int d, int m, int y)
{
    static int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
    y -= m < 3;
    return (y + y / 4 - y / 100 + y / 400 + t[m - 1] + d)
           % 7;
}
 
// Driver function to test above function
int main()
{
    int day = dayofweek(30, 8, 2010);
    printf("%d", day);
 
    return 0;
}


Java




// Java code to implement the approach
import java.util.*;
 
class FindDay {
    static int dayofweek(int d, int m, int y)
    {
        int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
        if (m < 3)
            y--;
        return (y + y / 4 - y / 100 + y / 400 + t[m - 1]
                + d)
            % 7;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int day = dayofweek(30, 8, 2010);
        System.out.println(day);
    }
}
/*Contributed and written by Aniket Dey*/


Python3




# Python3 program to find day
# of a given date
 
def dayofweek(d, m, y):
    t = [ 0, 3, 2, 5, 0, 3,
          5, 1, 4, 6, 2, 4 ]
    y -= m < 3
    return (( y + int(y / 4) - int(y / 100)
             + int(y / 400) + t[m - 1] + d) % 7)
 
# Driver Code
day = dayofweek(30, 8, 2010)
print(day)
 
# This code is contributed by Shreyanshi Arun.


C#




// C# program to find day of a given date
using System;
 
class GFG {
     
    static int dayofweek(int d, int m, int y)
    {
        int []t = { 0, 3, 2, 5, 0, 3, 5,
                            1, 4, 6, 2, 4 };
        y -= (m < 3) ? 1 : 0;
         
        return ( y + y/4 - y/100 + y/400
                         + t[m-1] + d) % 7;
    }
     
    // Driver Program to test above function
    public static void Main()
    {
        int day = dayofweek(30, 8, 2010);
         
        Console.Write(day);
    }
}
 
// This code is contributed by Sam007.


PHP




<?php
// PHP program to find
// day of a given date
function dayofweek($d, $m, $y)
{
    static $t = array(0, 3, 2, 5, 0, 3,
                      5, 1, 4, 6, 2, 4);
    $y -= $m < 3;
    return ($y + $y / 4 - $y / 100 +
            $y / 400 + $t[$m - 1] + $d) % 7;
}
 
// Driver Code
$day = dayofweek(30, 8, 2010);
echo $day;
 
// This code is contributed by mits.
?>


Javascript




<script>
 
// Javascript program to find day of a given date
 
function dayofweek(d, m, y)
{
    let t = [ 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 ];
    y -= (m < 3) ? 1 : 0;
    return ( y + y/4 - y/100 + y/400 + t[m-1] + d) % 7;
}
 
// Driver Code
 
    let day = dayofweek(30, 8, 2010);
    document.write(Math.round(day));
 
</script>


Output

1

Time Complexity: O(1)
Space Complexity: O(1), since no extra space has been taken.

See this for explanation of the above function.
References: 
http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week
This article is compiled by Dheeraj Jain and reviewed by GeeksforGeeks team.



Last Updated : 21 Oct, 2022
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