Best Way of Using JavaScript Date Methods

The JavaScript date functions manipulate time or retrieve information about it. This tutorial discusses the two categories of methods related to dates. Also, we explain how the JavaScript date object is created with the new Date() function. These date objects use a Unix Time Stamp.

You can always revisit our JavaScript date object and JavaScript date formats tutorials if needed. They're dedicated to JavaScript date object methods.

JavaScript Date: Main Tips

• Date methods make JavaScript get time or date, or set them.
• Date values can be expressed in years, months, days, hours, minutes, seconds or milliseconds.
• There are two categories of date methods: get methods and set methods.
• get methods return a part of a date.
• set methods specify in what form the parts of the date will be returned.
• By default, in computer languages, time is measured from January 1, 1970. That's called the Unix time.

get Methods

Date get methods return a part of the date you need. Take a look at the table to get a better idea:

getTime() Method

The method lets JavaScript get current time. It outputs the amount of milliseconds that have passed since January 1st, 1970:

var dt = new Date();
document.getElementById("dateOut").innerHTML = dt.getTime();

getFullYear() Method

The method lets JavaScript get current date year in a four digit number:

var dt = new Date();
document.getElementById("dateOut").innerHTML = dt.getFullYear();

getDay() Method

getDay() returns the weekday as a number:

var dt = new Date();
document.getElementById("dateOut").innerHTML = dt.getDay();

Note: This method returns a number from 0 to 6 that indicates the current week day, 0 representing Sunday.

set Methods

You are familiar with the ways to get date JavaScript, but sometimes you need to set it. Let's review set methods that help us set a part of the date:

setFullYear() Method

The method sets the date to be a specified date. The example below sets the date to January 1st, 2018.

var dt = new Date();
dt.setFullYear(2018, 0, 1);
document.getElementById("dateOutput").innerHTML = dt;

Note: just as weekdays, months are counted starting from 0. January is 0, December is 11.

setDate() Method

The method sets which day of the month it is (1-31).

var dt = new Date();
dt.setDate(14);
document.getElementById("dateOut").innerHTML = dt;

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Parsing Dates

There are different ways to make JavaScript get time or date. For example, Date.parse() method lets you parse a properly written date from a string and convert it to milliseconds:

var milSec = Date.parse("November 14, 1995");
document.getElementById("dateOut").innerHTML = milSec;

You can perform a reverse action as well. Convert the milliseconds back and voila - you get the date JavaScript:

var milSec = Date.parse("November 14, 1995");
var dt = new Date(milSec);
document.getElementById("dateOut").innerHTML = dt;

JavaScript Compare Dates

You can easily make JavaScript compare dates. The example below compares the date of today with November 14th, 1995:

var today, goodDay, textOut;
today = new Date();
goodDay = new Date();
goodDay.setFullYear(1995, 10, 14);

if (goodDay > today) {
    textOut= "Today is before November 14, 1995.";
} else {
    textOut= "Today is after November 14, 1995.";
}
document.getElementById("dateOut").innerHTML = textOut;

UTC Date Methods

There is a time standard used in the whole world to regulate time and clocks. It's called the Coordinated Universal Time, abbreviated to UTC. Keep in mind daylight savings do not affect it in any way.

Naturally, UTC is also important in programming. In JavaScript, you can use special date methods to work with UTC:

JavaScript Date: Summary

• You can use JavaScript date object methods to either set or get date values in years, months, days, hours, minutes, seconds or miliseconds.
• get methods return a part of a date.
• set methods specify the format of the date to be returned.
• You can make JavaScript get date according to Coordinated Universal Time (UTC).