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.
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 Codeint 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 functionint main(){ int day = dayofweek(30, 8, 2010); printf("%d", day); return 0;} |
Java
// Java code to implement the approachimport 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 datedef 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 Codeday = 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 datefunction 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 datefunction 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 neveropen team. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
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