Calculating the Number of Leap Years Using Moment.js

Leap years occur every four years to account for the extra time it takes for the Earth to orbit the Sun. However, there are also exceptions to the rule, such as years divisible by 100 but not divisible by 400, which are not leap years. In this tutorial, we will use Moment.js, a popular JavaScript library, to calculate the number of leap years between two given moments.

Table of Contents

• Prerequisites
• Calculating Leap Years
• Example
• Conclusion

Prerequisites

Before proceeding, you need to have a basic understanding of JavaScript and have Moment.js installed in your project. You can install Moment.js using the following command:

npm install moment

Once you have Moment.js available, you can start calculating the number of leap years.

Calculating Leap Years

Moment.js provides a feature-rich library for manipulating, parsing, and formatting dates and times in JavaScript. To calculate the number of leap years between two moments, we will make use of Moment.js’s isLeapYear function.

The isLeapYear function checks if a given year is a leap year or not. We can utilize this function to iterate over a range of years and count the number of leap years within that range.

Here is an example code snippet that calculates the number of leap years between two moments using Moment.js:

const moment = require('moment');

function countLeapYears(startMoment, endMoment) {
  let count = 0;

  for (let year = moment(startMoment).year(); year <= moment(endMoment).year(); year++) {
    if (moment(year).isLeapYear()) {
      count++;
    }
  }

  return count;
}

In the code snippet above, we define a function countLeapYears that takes two moments as parameters. Inside the function, we initialize a count variable to keep track of the number of leap years.

We then iterate over each year between the start and end moments using the .year() method. For each year, we check if it is a leap year using the .isLeapYear() function. If it is, we increment the count variable.

Finally, we return the total count of leap years.

Example

Now let’s see an example of how to use the countLeapYears function:

const moment = require('moment');

const startDate = moment('1990-01-01');
const endDate = moment('2022-12-31');

const leapYearsCount = countLeapYears(startDate, endDate);

console.log(`The number of leap years between ${startDate.format('YYYY-MM-DD')} and ${endDate.format('YYYY-MM-DD')} is ${leapYearsCount}.`);

In this example, we define the start date as January 1, 1990, and the end date as December 31, 2022. We then call the countLeapYears function, passing in the start and end moments.

The result is logged to the console, displaying the number of leap years between the two given moments.

Conclusion

Calculating the number of leap years between two moments can be easily achieved using Moment.js. By utilizing the isLeapYear function and iterating over the range of years, we can accurately determine the total count of leap years.

Moment.js is a powerful library with many other useful features for working with dates and times. Be sure to explore its documentation to take full advantage of its capabilities.