Day 30: Dates in JS - Part 1

Hello and welcome back to the 30th day of DailyJS, and our topic for this week would be Dates in JS.

Today we will discuss how can we create the Date objects in JS, and from tomorrow we will see various methods in the Date Object.

JavaScript Date objects represent a single moment in time in a platform-independent format. Date objects contain a Number that represents milliseconds since 1 January 1970 UTC. (source: MDN web docs)

The time - 00:00:00 UTC on 1 January 1970 - is also called as the UNIX epoch, and unix time is the number of seconds that have elapsed since that time.

Let’s take a look at the various ways of creating the Date Objects

Creating the Date Object

We use the Date() constructor to create a new Date object.

There are 4 ways to do so: (source: W3Schools)

new Date ()
new Date (year, month, day, hours, minutes, seconds, milliseconds)
new Date (miliseconds)
new Date (date string)

Let’s have a look at each one of them

Method #1

The first method is to use the Date constructor as it is, without any arguments. By doing so, we create a new date object having the present time and date.

new Date();

Example

/**
 * Dates in JS
 * Creating a Date Object
 */

const currentDate = Date ();
console.log ("Current date and Time is: ");
console.log (currentDate);

// Output: 
// Current Date and Time is: 
// Wed Feb 12 2020 16:09:43 GMT+0530 (India Standard Time)

Method #2

Using this method, we can create a new Date object with the given date and time.

The arguments are - year, month, day, hours, minutes, seconds, milliseconds.

But there is no need to provide all the arguments, we can use “1 to 7” number of arguments

new Date(year, month, day, hours, minutes, seconds, milliseconds)

Method #2 - Sample

// 1. With all 7 arguments
// year, month, day, hour, minute, second, and millisecond
var d7 = new Date (2020, 1, 12, 16, 20, 00, 00);

// 2. With 6 arguments
// year, month, day, hour, minute, second
var d6 = new Date (2020, 1, 12, 16, 20, 00);

// 3. With 5 arguments
// year, month, day, hour, and minute
var d5 = new Date (2020, 1, 12, 16, 20);

// 4. With 4 arguments
// year, month, day, and hour
var d4 = new Date (2020, 1, 12, 16);

// 5. With 3 arguments
// year, month, and day
var d3 = new Date (2020, 1, 12);

// 6. With 2 arguments
// year and month
var d2 = new Date (2020, 1);

// 7. With 1 argument
// With only one argument, it will be taken as milliseconds since the Epoch time
var d1 = new Date (1581514183500);
// Also, you can see that the third method is same as this method with 1 argument

Method #3

This method is same as the previous method with a single argument.

new Date(milliseconds)

Let’s see an example -

/**
 * Dates in JS
 * Creating a Date Object - Method 3
 */

// Syntax - new Date (miliseconds)
var date = new Date (1581514183500);
console.log (date);

Method #4

We can create a new date object by providing the date as a string.

new Date (date-string);