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diff --git a/Project-Euler/Problem019.js b/Project-Euler/Problem019.js
 /*
 You are given the following information, but you may prefer to do some research for yourself.

  * 1 Jan 1900 was a Monday.
  * Thirty days has September,
    April, June and November.
    All the rest have thirty-one,
    Saving February alone,
    Which has twenty-eight, rain or shine.
    And on leap years, twenty-nine.
  * A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.

 How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
 */

 export function countingSundays () {
  let numberOfSundays = 0
  let dow = 2

  // The number od days in each month of the year
  const months = [31, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

  for (let y = 1901; y <= 2000; y++) {
    // Calculate the number of Days in February this year
    months[1] = 28 + ((y % 4 === 0 && y % 100 !== 0) || y % 400 === 0)

    for (const month of months) {
      dow = dow + (month % 7)

      if (dow % 7 === 0) {
        numberOfSundays++
      }
    }
  }

  return numberOfSundays
 }
diff --git a/Project-Euler/test/Problem019.test.js b/Project-Euler/test/Problem019.test.js
 import { countingSundays } from '../Problem019.js'

 describe('checking Counting Sundays', () => {
  // Project Euler Condition Check
  test('Test Euler Condition', () => {
    expect(countingSundays()).toBe(171)
  })
 })
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,37 @@
		/*
		You are given the following information, but you may prefer to do some research for yourself.

		* 1 Jan 1900 was a Monday.
		* Thirty days has September,
		April, June and November.
		All the rest have thirty-one,
		Saving February alone,
		Which has twenty-eight, rain or shine.
		And on leap years, twenty-nine.
		* A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.

		How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
		*/

		export function countingSundays () {
		let numberOfSundays = 0
		let dow = 2

		// The number od days in each month of the year
		const months = [31, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

		for (let y = 1901; y <= 2000; y++) {
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		// Calculate the number of Days in February this year
		months[1] = 28 + ((y % 4 === 0 && y % 100 !== 0) \|\| y % 400 === 0)

		for (const month of months) {
		dow = dow + (month % 7)

		if (dow % 7 === 0) {
		numberOfSundays++
		}
		}
		}

		return numberOfSundays
		}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,8 @@
		import { countingSundays } from '../Problem019.js'

		describe('checking Counting Sundays', () => {
		// Project Euler Condition Check
		test('Test Euler Condition', () => {
		expect(countingSundays()).toBe(171)
		})
		})