Flash cards
Review the key moves
What is the main idea behind JavaScript Dates?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___ d = new Date();Put the learning moves in the order that makes the concept easiest to apply.
JavaScript Date Objects let us work with dates:
Examples
const d = new Date();Date objects are static. The "clock" is not "running".
The computer clock is ticking, date objects are not.
JavaScript Date Output
By default, JavaScript will use the browser's time zone and display a date as a full text string:
You will learn much more about how to display dates, later in this tutorial.
Creating Date Objects
Date objects are created with the new Date() constructor.
There are 9 ways to create a new date object:
new Date()
new Date(
date string
)
new Date(
year,month
)
new Date(
year,month,day
)
new Date(
year,month,day,hours
)
new Date(
year,month,day,hours,minutes
)
new Date(
year,month,day,hours,minutes,seconds
)
new Date(
year,month,day,hours,minutes,seconds,ms
)
new Date(
milliseconds
)JavaScript new Date()
new Date() creates a date object with the current date and time :
Example
const d = new Date();new Date( date string )
new Date( date string ) creates a date object from a date string :
Examples
const d = new Date("October 13, 2014 11:13:00");Date string formats are described in the next chapter.
new Date( year, month, ... )
new Date( year, month, ... ) creates a date object with a specified date and time .
7 numbers specify year, month, day, hour, minute, second, and millisecond (in that order):
Example
const d = new Date(2018, 11, 24, 10, 33, 30, 0);JavaScript counts months from 0 to 11 :
January = 0 .
December = 11 .
Specifying a month higher than 11, will not result in an error but add the overflow to the next year:
Runnable example
const d = new Date(2018, 15, 24, 10, 33, 30);Specifying a day higher than max, will not result in an error but add the overflow to the next month:
Runnable example
const d = new Date(2018, 5, 35, 10, 33, 30);Using 6, 4, 3, or 2 Numbers
6 numbers specify year, month, day, hour, minute, second:
Example
const d = new Date(2018, 11, 24, 10, 33, 30);5 numbers specify year, month, day, hour, and minute:
Example
const d = new Date(2018, 11, 24, 10, 33);4 numbers specify year, month, day, and hour:
Example
const d = new Date(2018, 11, 24, 10);3 numbers specify year, month, and day:
Example
const d = new Date(2018, 11, 24);2 numbers specify year and month:
Example
const d = new Date(2018, 11);You cannot omit month. If you supply only one parameter it will be treated as milliseconds.
Example
const d = new Date(2018);One and two digit years will be interpreted as 19xx:
Example
const d = new Date(99, 11, 24);Example
const d = new Date(9, 11, 24);JavaScript Stores Dates as Milliseconds
JavaScript stores dates as number of milliseconds since January 01, 1970.
Zero time is January 01, 1970 00:00:00 UTC .
One day (24 hours) is 86 400 000 milliseconds.
Now the time is: milliseconds past January 01, 1970
new Date( milliseconds )
new Date( milliseconds ) creates a new date object as milliseconds plus zero time:
Examples
const d = new Date(100000000000);Date Methods
When a date object is created, a number of methods allow you to operate on it.
Date methods allow you to get and set the year, month, day, hour, minute, second, and millisecond of date objects, using either local time or UTC (universal, or GMT) time.
Date methods and time zones are covered in the next chapters.
Displaying Dates
JavaScript will (by default) output dates using the toString() method. This is a string representation of the date, including the time zone. The format is specified in the ECMAScript specification:
Example
When you display a date object in HTML, it is automatically converted to a string, with the toString() method.
Example
const d = new Date();
d.toString();The toDateString() method converts a date to a more readable format:
Example
const d = new Date();
d.toDateString();The toUTCString() method converts a date to a string using the UTC standard:
Example
const d = new Date();
d.toUTCString();The toISOString() method converts a date to a string using the ISO standard:
Example
const d = new Date();
d.toISOString();Learn More
JavaScript Date Formats
JavaScript Date Get Methods
JavaScript Date Set Methods
JavaScript Date Reference