This Moment.js tutorial shows how to work with data and time in JavaScript with the Moment.js module. Moment.js Moment.js is a lightweight JavaScript date library for parsing, validating, manipulating, and formatting dates. In this tutorial, we work with Moment.js in a Node application. There is a similar Day.js library, which is covered in the Day.js tutorial. Setting up Moment.js First, we install Moment.js. $ npm init We initiate a new Node application. $ npm i moment We install Moment.js with command. npm i moment Moment.js today's date In the first example, we get today's date with Moment.js. today.js const moment = require('moment');

let now = moment();
console.log(now.format()); The example prints today's date and time. const moment = require('moment'); We load the Moment.js library. let now = moment(); We get the current local DateTime object with . moment console.log(now.format()); We format the output with . By default, we get a long DateTime format. format $ node today.js 
2018-07-01T16:32:53+02:00 This is the ISO standard format. The date and time parts are separated by the T character. The string is ended with a time zone. Creating Moment.js objects We can use several ways to create date and time Moment.js objects. These objects have to be formatted later to human-readable format. //create_objects.js

const moment = require('moment');

let d1 = moment("2018-06-03");
console.log(d1.format('ll'));

let d2 = moment([2017, 11, 23]);
console.log(d2.format('ll'));

let d3 = moment({ year :2010, month :3, day :5, 
    hour :15, minute :10, second :3, millisecond :123});
console.log(d3.format('ll'));

let d4 = moment(1530471537000);
console.log(d4.format('ll'));

let d5 = moment(new Date(2011, 11, 22));
console.log(d5.format('ll')); The example creates date and time objects in five different ways. let d1 = moment("2018-06-03"); We create a moment object from a string. let d2 = moment([2017, 11, 23]);
console.log(d2.format('ll')); Here a moment object is created from an array. let d3 = moment({ year :2010, month :3, day :5, 
    hour :15, minute :10, second :3, millisecond :123});
console.log(d3.format('ll')); We can use JSON objects to create moment objects. let d4 = moment(1530471537000);
console.log(d4.format('ll')); We use a UNIX timestamp (in milliseconds) to define a moment object. let d5 = moment(new Date(2011, 11, 22));
console.log(d5.format('ll')); Finally, we use a JavaScript built-in Date object to define a moment object. $ node create_moment_objects.js 
Jun 3, 2018
Dec 23, 2017
Apr 5, 2010
Jul 1, 2018
Dec 22, 2011 Moment.js Calculating datetime Difference With the function, we can calculate the difference between two datetime objects. diff difference.js const moment = require('moment');

let d1 = moment('2018-06-12');
let d2 = moment('2018-06-28');

let days = d2.diff(d1, 'days');
console.log(`Difference in days: ${days}`);

let hours = d2.diff(d1, 'hours');
console.log(`Difference in hours: ${hours}`); The example calculates the difference between two-moment objects in days and hours. let days = d2.diff(d1, 'days'); The second parameter tells that the output will be in days. $ node difference.js 
Difference in days: 16
Difference in hours: 384 The Battle of Borodino was a battle fought on 7 September 1812 in the Napoleonic Wars during the French invasion of Russia. borodino.js const moment = require('moment');

let borodinoBattle = moment('1812-09-07');

let now = moment();
let days = now.diff(borodinoBattle, 'days');

console.log(`On ${now.format('ll')}, ${days} days have passed since the Borodino battle.`); In the example, we calculate the number of days passed since then. $ node borodino.js 
On Jul 3, 2018, 75174 days have passed since the Borodino battle. This is a sample output. Moment.js DateTime arithmetic The function is used to add date and time to the moment object and the function subtracts date and time from the moment object. add subtract add_sub.js const moment = require('moment');

let now = moment();

console.log(`Now: ${now.format('ll')}`);

now.add('3', 'days');
console.log(`Adding three days: ${now.format('ll')}`);

now.subtract('2', 'years');
console.log(`Subtracting 2 years: ${now.format('ll')}`); In the example, we add three days and subtract two years. now.add('3', 'days'); ... now.subtract('2', 'years'); The second parameter of the and methods is the unit type. add subtract $ node add_sub.js 
Now: Jul 1, 2018
Adding three days: Jul 4, 2018
Subtracting 2 years: Jul 4, 2016 Moment.js Datetime Parts In the following example, we get the parts of the current DateTime. parts.js const moment = require('moment');

let now = moment();

let year = now.get('year');
let month = now.get('month');  // 0 to 11
let date = now.get('date');
let hour = now.get('hour');
let minute = now.get('minute');
let second = now.get('second');
let millisecond = now.get('millisecond');

console.log("Year: " + year);
console.log("Month: " + month);
console.log("Date: " + date);
console.log("Hour: " + hour);
console.log("Minute: " + minute);
console.log("Second: " + second);
console.log("Millisecond: " + millisecond); The example computes the current DateTime. We get the year, month, date, hour, minute, second, and millisecond parts of the DateTime. $ node parts.js 
Year: 2018
Month: 6
Date: 2
Hour: 18
Minute: 10
Second: 3
Millisecond: 329 This is a sample output. Moment.js Day of the week, month, year The following example calculates the day of the week, month, and year. dayof.js const moment = require('moment');

let now = moment();

console.log("Day of week: " + now.weekday()); 
console.log("Day of month: " + now.date()); 
console.log("Day of year: " + now.dayOfYear()); The returns the day of week, the returns the day of month, and the returns the day of year. weekday date dayOfYear $ node main.js 
Day of week: 1
Day of month: 2
Day of year: 183 Moment.js week of year, quarter, weeks in year In the following example, we get the week of the year, the quarter of the year, and the number of weeks in the year. weeks_quarter.js const moment = require('moment');

let now = moment();

console.log("Week of year: " + now.week());
console.log("Quarter of year: " + now.quarter());
console.log("Weeks in year: " + now.weeksInYear()); The method returns the week of the year, the returns the quarter of the year, and the returns the number of weeks in the year. week quarter weeksInYear $ node weeks_quarter.js 
Week of year: 27
Quarter of year: 3
Weeks in year: 52 This is a sample output. Moment.js relative DateTime We can compute relative DateTime with , , and functions. fromNow startOf endOf relative_time.js const moment = require('moment');

let day = moment().startOf('year');
let now = moment();

let days = now.diff(day, 'days');

console.log(`${days} have passed since the start of the year.`);

let val = moment().endOf('day');
let mins = val.diff(now, 'minutes');

console.log(`The day will end in ${mins} minutes.`);

let day2 = moment("2028-12-20")
let diff = day2.fromNow();

console.log(`The day will come ${diff}.`); The example uses the aforementioned functions. let day = moment().startOf('year');
let now = moment();

let days = now.diff(day, 'days'); Here we calculate the number of days which have passed since the beginning of the year. let val = moment().endOf('day');
let mins = val.diff(now, 'minutes'); These lines calculate the number of minutes till midnight. let day2 = moment("2028-12-20")
let diff = day2.fromNow(); Here we get the number of years until the specified day. $ node relative_time.js 
182 have passed since the start of the year.
The day will end in 360 minutes.
The day will come in 10 years. Moment.js checking validity We can use the method to check if the date and time object is valid. isValid validity.js const moment = require('moment');

let day1 = moment('2018-12-12');
let day2 = moment('2018-13-12');

if (day1.isValid()) {

    console.log("Day is valid");
} else {
    
    console.log("Day is not valid");
}

if (day2.isValid()) {

    console.log("Day is valid");
} else {
    
    console.log("Day is not valid");
} The example checks the validity of two days. Moment.js date queries The and functions can be used to determine if a date is before or after another date. isBefore isAfter date_queries.js const moment = require('moment');

let d1 = moment("2018-05-19");
let d2 = moment("2018-05-20");
let d3 = moment("2018-05-22");

if (d1.isAfter(d2)) {

    console.log(`${d1.format('ll')} is after ${d2.format('ll')}`);
} else {

    console.log(`${d1.format('ll')} is before ${d2.format('ll')}`);
}

if (d2.isBefore(d3)) {

    console.log(`${d2.format('ll')} is before ${d3.format('ll')}`);
} else {

    console.log(`${d2.format('ll')} is after ${d3.format('ll')}`);
} In the example, we compare three dates using and functions. isBefore isAfter $ node date_queries.js 
May 19, 2018 is before May 20, 2018
May 20, 2018 is before May 22, 2018 The function checks if a date is in the given date range. isBetween between.js const moment = require('moment');

let d1 = moment("2018-05-19");

if (d1.isBetween('2018-05-10', '2018-05-25')) {

    console.log("The day is within the date range");
} The example uses the function to determine if a date is within the specified date range. isBetween Moment.js unix time Unix time is the number of seconds since the Unix epoch. The function returns the value of time in seconds since 0 hours, 0 minutes, 0 seconds, January 1, 1970, Coordinated Universal Time. unix unixtime.js const moment = require('moment');

let unixTime = moment().unix();
console.log(unixTime);

let unixTime2 = moment(1000);
console.log(unixTime2.format('MM-DD-YYYY')); In the example, we get the current Unix time and convert Unix time 1 s to human readable format. let unixTime = moment().unix(); We get the Unix time with function. The returned value is the number of seconds elapsed from the start of the Unix Epoch. unix let unixTime2 = moment(1000);
console.log(unixTime2.format('MM-DD-YYYY')); We get the unix time of 1 s and output it in the given format. $ node unixtime.js 
1530606134
01-01-1970 Moment.js Parsing date and time We can parse a string representation of date and time bypassing the date and time format to the function. moment parse.js const moment = require('moment');

let day = "03/04/2008";
let parsed = moment(day, "DD/MM/YYYY");

console.log(parsed.format('ll')); In the example, we parse a non-standard date and time string. We pass the expected format as a second parameter of the function. moment Moment.js localized date and time With the function, we can set the locale in which we get the output. locale localized.js const moment = require('moment');

moment.locale('sk');
let now = moment();
console.log(now.format('LLLL'));

moment.locale('de');
now = moment();
console.log(now.format('LLLL'));

moment.locale('hu');
now = moment();
console.log(now.format('LLLL')); In the example, we print the current moment in three different locales. $ node localized.js 
nedeľa 1. júl 2018 22:21
Sonntag, 1. Juli 2018 22:21
2018. július 1., vasárnap 22:21 We have Slovak, German, and Hungarian date and time outputs of the current moment. Universal time Our planet is a sphere; it revolves around its axis. The Earth rotates towards the east, so the Sun rises at different times in different locations. The Earth rotates once in about 24 hours. The world was therefore divided into 24 time zones. In each time zone, there is a different local time. This local time is often further modified by daylight saving. There is a pragmatic need for one global time. One global time helps to avoid confusion about time zones and daylight saving time. The UTC (Universal Coordinated time) was chosen to be the primary time standard. UTC is used in aviation, weather forecasts, flight plans, air traffic control clearances, and maps. Unlike local time, UTC does not change with a change of seasons. utc.js const moment = require('moment');

let localTime = moment();
console.log(localTime.format());

let utcTime = moment().utc();
console.log(utcTime.format('lll')); The example prints the current UTC time and the local time. let utcTime = moment().utc(); The universal time is retrieved with . utc $ node utc.js 
2018-07-01T21:15:17+02:00
Jul 1, 2018 7:15 PM In our case, the difference between the local and universal time is two hours. One hour is for the time zone and another hour for the daylight saving. Moment.js leap year A leap year is a year containing an additional day. The reason for an extra day in the calendar is the difference between the astronomical and the calendar year. leap_year.js const moment = require('moment');

// Assume year >= 1582 in the Gregorian calendar.

let years = [ 2000, 2002, 2004, 2008, 2012, 2016, 2020,
    1900, 1800, 1600 ];

for (year of years) {

    let ym = moment([year]);

    if (ym.isLeapYear()) {

        console.log(`${year} is a leap year`);
    } else {
        
        console.log(`${year} is not a leap year`);
    }
} In the example, we have an array of years. We determine which years are leap years. if (ym.isLeapYear()) { We determine if a year is a leap year with the function. isLeapYear $ node leap_year.js 
2000 is a leap year
2002 is not a leap year
2004 is a leap year
2008 is a leap year
2012 is a leap year
2016 is a leap year
2020 is a leap year
1900 is not a leap year
1800 is not a leap year
1600 is a leap year In this tutorial, we have worked with date and time in JavaScript using the library Moment.js

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