diff --git a/Conversions/DateToDay.js b/Conversions/DateToDay.js
index 8683bdec4b..d295ff25a9 100644
--- a/Conversions/DateToDay.js
+++ b/Conversions/DateToDay.js
@@ -4,59 +4,38 @@
 The DateToDay method takes a date in string format and
 returns the name of a day. The approach behind this method
 is very simple, we first take a string date and check
- whether their date is valid or not, if the date is valid
- then we do this But apply the algorithm shown below. The
- algorithm shown below gives us the number of the day and
- finally converts it to the name of the day.
-
- Algorithm & Explanation : https://cs.uwaterloo.ca/~alopez-o/math-faq/node73.html
+ whether their date is valid or not, if the date is not valid
+ then we return a type error, else we apply Zeller's congruence.
+ Algorithm & Explanation : https://www.geeksforgeeks.org/zellers-congruence-find-day-date/
 */
 
-// March is taken as the first month of the year.
-const calcMonthList = {
- 1: 11,
- 2: 12,
- 3: 1,
- 4: 2,
- 5: 3,
- 6: 4,
- 7: 5,
- 8: 6,
- 9: 7,
- 10: 8,
- 11: 9,
- 12: 10
-}
-
-// show the week day in a number : Sunday - Saturday => 0 - 6
-const daysNameList = { // weeks-day
- 0: 'Sunday',
- 1: 'Monday',
- 2: 'Tuesday',
- 3: 'Wednesday',
- 4: 'Thursday',
- 5: 'Friday',
- 6: 'Saturday'
-}
-
+// days in a week : Sunday - Saturday => 0 - 6
+const daysNameList = [
+ 'Sunday',
+ 'Monday',
+ 'Tuesday',
+ 'Wednesday',
+ 'Thursday',
+ 'Friday',
+ 'Saturday'
+]
 const DateToDay = (date) => {
 // firstly, check that input is a string or not.
 if (typeof date !== 'string') {
 return new TypeError('Argument is not a string.')
 }
 // extract the date
- const [day, month, year] = date.split('/').map((x) => Number(x))
+ let [day, month, year] = date.split('/').map((x) => Number(x))
 // check the data are valid or not.
 if (day < 0 &#124;&#124; day> 31 &#124;&#124; month> 12 &#124;&#124; month < 0) { return new TypeError('Date is not valid.') } - // divide year to century and yearDigit value. - const yearDigit = (year % 100) + // count Jan & Feb as months 13 & 14 of the previous year + if (month < 3) { year--; month += 12 } const century = Math.floor(year / 100) - // Apply the algorithm shown above - const weekDay = Math.abs((day + Math.floor((2.6 * calcMonthList[month]) - 0.2) - (2 * century) + yearDigit + Math.floor(yearDigit / 4) + Math.floor(century / 4)) % 7) - // return the weekDay name. - return daysNameList[weekDay] + year %= 100 + const weekDay = (year + Math.floor(year / 4) + Math.floor(century / 4) - 2 * century + Math.floor((26 * (month + 1)) / 10) + day - 1) + return daysNameList[(weekDay + 7) % 7] } // Example : DateToDay("18/12/2020") => Friday
diff --git a/Conversions/test/DateToDay.test.js b/Conversions/test/DateToDay.test.js
index a932dff08c..d5cec6c4fa 100644
--- a/Conversions/test/DateToDay.test.js
+++ b/Conversions/test/DateToDay.test.js
@@ -2,7 +2,7 @@ import { DateToDay } from '../DateToDay'
 
 test('The date 18/02/2001 is Monday', () => {
 const res = DateToDay('18/02/2001')
- expect(res).toBe('Monday')
+ expect(res).toBe('Sunday')
 })
 
 test('The date 18/12/2020 is Friday', () => {
@@ -16,5 +16,5 @@ test('The date 12/12/2012 is Wednesday', () => {
 })
 test('The date 01/01/2001 is Friday', () => {
 const res = DateToDay('01/01/2001')
- expect(res).toBe('Friday')
+ expect(res).toBe('Monday')
 })
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