JavaScript Date Objects
JavaScript Date Object lets us work with dates:
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 4 ways to create a new date object:
new Date()
new Date(year, month, day, hours, minutes, seconds, milliseconds)
new Date(milliseconds)
new Date(date string)
new Date()
new Date() creates a new date object with the current date and time:
Date objects are static. The computer time is ticking, but date objects are not.
new Date(year, month, ...)
new Date(year, month, ...) creates a new date object with a specified date and time.
7 numbers specify year, month, day, hour, minute, second, and millisecond (in that order):
Note: JavaScript counts months from 0 to 11.
January is 0. December is 11.
6 numbers specify year, month, day, hour, minute, second:
5 numbers specify year, month, day, hour, and minute:
4 numbers specify year, month, day, and hour:
3 numbers specify year, month, and day:
2 numbers specify year and month:
You cannot omit month. If you supply only one parameter it will be treated as milliseconds.
Previous Century
One and two digit years will be interpreted as 19xx:
new Date(dateString)
new Date(dateString) creates a new date object from a date string:
Date strings are described in the next chapter.
JavaScript Stores Dates as Milliseconds
JavaScript stores dates as number of milliseconds since January 01, 1970, 00:00:00 UTC (Universal Time Coordinated).
Zero time is January 01, 1970 00:00:00 UTC.
Now the time is: milliseconds past January 01, 1970
new Date(milliseconds)
new Date(milliseconds) creates a new date object as zero time plus milliseconds:
01 January 1970 plus 100 000 000 000 milliseconds is approximately 03 March 1973:
January 01 1970 minus 100 000 000 000 milliseconds is approximately October 31 1966:
One day (24 hours) is 86 400 000 milliseconds.
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 in full text string format:
When you display a date object in HTML, it is automatically converted to a
string, with the toString() method.
Example
d = new Date();
document.getElementById("demo").innerHTML = d;
Same as:
d = new Date();
document.getElementById("demo").innerHTML = d.toString();
Try it Yourself »
The toUTCString() method converts a date to a UTC string (a date display
standard).
Example
var d = new Date();
document.getElementById("demo").innerHTML = d.toUTCString();
Try it Yourself »
The toDateString() method converts a date to a more readable
format:
Example
var d = new Date();
document.getElementById("demo").innerHTML = d.toDateString();
Try it Yourself »
