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---
id: 5900f37f1000cf542c50fe92
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title: 'Problem 19: Counting Sundays'
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challengeType: 5
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forumTopicId: 301827
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dashedName: problem-19-counting-sundays
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---
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# --description--
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You are given the following information, but you may prefer to do some research for yourself.
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< ul >
< li > 1 Jan 1900 was a Monday.< / li >
< li > Thirty days has September,< br > April, June and November.< br > All the rest have thirty-one,< br > Saving February alone,< br > Which has twenty-eight, rain or shine.< br > And on leap years, twenty-nine.< / li >
< li > A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.< / li >
< / ul >
How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
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# --hints--
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`countingSundays(1943, 1946)` should return a number.
```js
assert(typeof countingSundays(1943, 1946) === 'number');
```
`countingSundays(1943, 1946)` should return 6.
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```js
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assert.strictEqual(countingSundays(1943, 1946), 6);
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```
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`countingSundays(1995, 2000)` should return 10.
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```js
assert.strictEqual(countingSundays(1995, 2000), 10);
```
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`countingSundays(1901, 2000)` should return 171.
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```js
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assert.strictEqual(countingSundays(1901, 2000), 171);
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```
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# --seed--
## --seed-contents--
```js
function countingSundays(firstYear, lastYear) {
return true;
}
countingSundays(1943, 1946);
```
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# --solutions--
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```js
function countingSundays(firstYear, lastYear) {
let sundays = 0;
for (let year = firstYear; year < = lastYear; year++) {
for (let month = 0; month < = 11; month++) {
const thisDate = new Date(year, month, 1);
if (thisDate.getDay() === 0) {
sundays++;
}
}
}
return sundays;
}
```