---
id: 5900f37f1000cf542c50fe92
title: 'Problem 19: Counting Sundays'
challengeType: 5
forumTopicId: 301827
dashedName: problem-19-counting-sundays
---
# --description--
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)?
# --hints--
`countingSundays(1943, 1946)` should return a number.
```js
assert(typeof countingSundays(1943, 1946) === 'number');
```
`countingSundays(1943, 1946)` should return 6.
```js
assert.strictEqual(countingSundays(1943, 1946), 6);
```
`countingSundays(1995, 2000)` should return 10.
```js
assert.strictEqual(countingSundays(1995, 2000), 10);
```
`countingSundays(1901, 2000)` should return 171.
```js
assert.strictEqual(countingSundays(1901, 2000), 171);
```
# --seed--
## --seed-contents--
```js
function countingSundays(firstYear, lastYear) {
return true;
}
countingSundays(1943, 1946);
```
# --solutions--
```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;
}
```