Date

Summary

Creates a JavaScript Date instance that represents a single moment in time. Date objects are based on a time value that is the number of milliseconds since 1 January, 1970 UTC.

Constructor

new Date();
new Date(value);
new Date(dateString);
new Date(year, month, day, hour, minute, second, millisecond);

Note: Note that JavaScript Date objects can only be instantiated by calling JavaScript Date as a constructor: calling it as a regular function (i.e. without the new operator) will return a string rather than a Date object; unlike other JavaScript object types, JavaScript Date objects have no literal syntax.

Date constructor parameters

Note: Where Date is called as a constructor with more than one argument, if values are greater than their logical range (e.g. 13 is provided as the month value or 70 for the minute value), the adjacent value will be adjusted. E.g.  new Date(2013,13,1) is equivalent to new Date(2014,1,1), both create a date for 2014-02-01 (note that the month is 0-based).  Similarly for other values: new Date(2013,2,1,0,70) is equivalent to new Date(2013,2,1,1,10) which both create a date for 2013-03-01T01:10:00.

value
Integer value representing the number of milliseconds since 1 January 1970 00:00:00 UTC (Unix Epoch).
dateString
String value representing a date. The string should be in a format recognized by the Date.parse() method (IETF-compliant RFC 2822 timestamps and also a version of ISO8601).
year
Integer value representing the year. Values from 0 to 99 map to the years 1900 to 1999. See the example below.
month
Integer value representing the month, beginning with 0 for January to 11 for December.
day
Integer value representing the day of the month.
hour
Integer value representing the hour of the day.
minute
Integer value representing the minute segment of a time.
second
Integer value representing the second segment of a time.
millisecond
Integer value representing the millisecond segment of a time.

Description

  • If no arguments are provided, the constructor creates a JavaScript Date object for the current date and time according to system settings.
  • If at least two arguments are supplied, missing arguments are either set to 1 (if day is missing) or 0 for all others.
  • The JavaScript date is  based on a time value that is milliseconds since midnight 01 January, 1970 UTC. A day holds 86,400,000 milliseconds. The JavaScript Date object range is -100,000,000 days to 100,000,000 days relative to 01 January, 1970 UTC.
  • The JavaScript Date object provides uniform behavior across platforms. The time value can be passed between systems to represent the same moment in time and if used to create a local date object, will reflect the local equivalent of the time.
  • The JavaScript Date object supports a number of UTC (universal) methods, as well as local time methods. UTC, also known as Greenwich Mean Time (GMT), refers to the time as set by the World Time Standard. The local time is the time known to the computer where JavaScript is executed.
  • Invoking JavaScript Date as a function (i.e., without the new operator) will return a string representing the current date and time.

Properties

For properties available on Date instances, see Properties of Date instances.

Date.prototype
Allows the addition of properties to a JavaScript Date object.
Date.length
The value of Date.length is 7.

Properties inherited from Function:

Methods

For methods available on Date instances, see Methods of Date instances.

Date.now()
Returns the numeric value corresponding to the current time - the number of milliseconds elapsed since 1 January 1970 00:00:00 UTC.
Date.parse()
Parses a string representation of a date and returns the number of milliseconds since 1 January, 1970, 00:00:00, local time.
Date.UTC()
Accepts the same parameters as the longest form of the constructor (i.e. 2 to 7) and returns the number of milliseconds since 1 January, 1970, 00:00:00 UTC.

Methods inherited from Function:

JavaScript Date instances

All Date instances inherit from Date.prototype. The prototype object of the Date constructor can be modified to affect all Date instances.

Methods

Getter

Date.prototype.getDate()
Returns the day of the month (1-31) for the specified date according to local time.
Date.prototype.getDay()
Returns the day of the week (0-6) for the specified date according to local time.
Date.prototype.getFullYear()
Returns the year (4 digits for 4-digit years) of the specified date according to local time.
Date.prototype.getHours()
Returns the hour (0-23) in the specified date according to local time.
Date.prototype.getMilliseconds()
Returns the milliseconds (0-999) in the specified date according to local time.
Date.prototype.getMinutes()
Returns the minutes (0-59) in the specified date according to local time.
Date.prototype.getMonth()
Returns the month (0-11) in the specified date according to local time.
Date.prototype.getSeconds()
Returns the seconds (0-59) in the specified date according to local time.
Date.prototype.getTime()
Returns the numeric value of the specified date as the number of milliseconds since January 1, 1970, 00:00:00 UTC (negative for prior times).
Date.prototype.getTimezoneOffset()
Returns the time-zone offset in minutes for the current locale.
Date.prototype.getUTCDate()
Returns the day (date) of the month (1-31) in the specified date according to universal time.
Date.prototype.getUTCDay()
Returns the day of the week (0-6) in the specified date according to universal time.
Date.prototype.getUTCFullYear()
Returns the year (4 digits for 4-digit years) in the specified date according to universal time.
Date.prototype.getUTCHours()
Returns the hours (0-23) in the specified date according to universal time.
Date.prototype.getUTCMilliseconds()
Returns the milliseconds (0-999) in the specified date according to universal time.
Date.prototype.getUTCMinutes()
Returns the minutes (0-59) in the specified date according to universal time.
Date.prototype.getUTCMonth()
Returns the month (0-11) in the specified date according to universal time.
Date.prototype.getUTCSeconds()
Returns the seconds (0-59) in the specified date according to universal time.
Date.prototype.getYear()
Returns the year (usually 2-3 digits) in the specified date according to local time. Use getFullYear() instead.

Setter

Date.prototype.setDate()
Sets the day of the month for a specified date according to local time.
Date.prototype.setFullYear()
Sets the full year (e.g. 4 digits for 4-digit years) for a specified date according to local time.
Date.prototype.setHours()
Sets the hours for a specified date according to local time.
Date.prototype.setMilliseconds()
Sets the milliseconds for a specified date according to local time.
Date.prototype.setMinutes()
Sets the minutes for a specified date according to local time.
Date.prototype.setMonth()
Sets the month for a specified date according to local time.
Date.prototype.setSeconds()
Sets the seconds for a specified date according to local time.
Date.prototype.setTime()
Sets the Date object to the time represented by a number of milliseconds since January 1, 1970, 00:00:00 UTC, allowing for negative numbers for times prior.
Date.prototype.setUTCDate()
Sets the day of the month for a specified date according to universal time.
Date.prototype.setUTCFullYear()
Sets the full year (e.g. 4 digits for 4-digit years) for a specified date according to universal time.
Date.prototype.setUTCHours()
Sets the hour for a specified date according to universal time.
Date.prototype.setUTCMilliseconds()
Sets the milliseconds for a specified date according to universal time.
Date.prototype.setUTCMinutes()
Sets the minutes for a specified date according to universal time.
Date.prototype.setUTCMonth()
Sets the month for a specified date according to universal time.
Date.prototype.setUTCSeconds()
Sets the seconds for a specified date according to universal time.
Date.prototype.setYear()
Sets the year (usually 2-3 digits) for a specified date according to local time. Use setFullYear() instead.

Conversion getter

Date.prototype.toDateString()
Returns the "date" portion of the Date as a human-readable string.
Date.prototype.toISOString()
Converts a date to a string following the ISO 8601 Extended Format.
Date.prototype.toJSON()
Returns a string representing the Date using toISOString(). Intended for use by JSON.stringify().
Date.prototype.toGMTString()
Returns a string representing the Date based on the GMT (UT) time zone. Use toUTCString() instead.
Date.prototype.toLocaleDateString()
Returns a string with a locality sensitive representation of the date portion of this date based on system settings.
Date.prototype.toLocaleFormat()
Converts a date to a string, using a format string.
Date.prototype.toLocaleString()
Returns a string with a locality sensitive representation of this date. Overrides the Object.prototype.toLocaleString() method.
Date.prototype.toLocaleTimeString()
Returns a string with a locality sensitive representation of the time portion of this date based on system settings.
Date.prototype.toSource()
Returns a string representing the source for an equivalent Date object; you can use this value to create a new object. Overrides the Object.prototype.toSource() method.
Date.prototype.toString()
Returns a string representing the specified Date object. Overrides the Object.prototype.toString() method.
Date.prototype.toTimeString()
Returns the "time" portion of the Date as a human-readable string.
Date.prototype.toUTCString()
Converts a date to a string using the UTC timezone.
Date.prototype.valueOf()
Returns the primitive value of a Date object. Overrides the Object.prototype.valueOf() method.

Examples

Example: Several ways to create a Date object

The following examples show several ways to create JavaScript dates:

var today = new Date();
var birthday = new Date("December 17, 1995 03:24:00");
var birthday = new Date("1995-12-17T03:24:00");
var birthday = new Date(1995,11,17);
var birthday = new Date(1995,11,17,3,24,0);

Example: Two digit years map to 1900 - 1999

In order to create and get dates between the years 0 and 99 the Date.prototype.setFullYear() and Date.prototype.getFullYear() methods should be used.

var date = new Date(98, 1); // Sun Feb 01 1998 00:00:00 GMT+0000 (GMT)

// Deprecated method, 98 maps to 1998 here as well
date.setYear(98);           // Sun Feb 01 1998 00:00:00 GMT+0000 (GMT)

date.setFullYear(98);       // Sat Feb 01 0098 00:00:00 GMT+0000 (BST)

Example: Calculating elapsed time

The following examples show how to determine the elapsed time between two JavaScript dates:

// using Date objects
var start = Date.now();

// the event to time goes here:
doSomethingForALongTime();
var end = Date.now();
var elapsed = end - start; // elapsed time in milliseconds
// using built-in methods
var start = new Date();

// the event to time goes here:
doSomethingForALongTime();
var end = new Date();
var elapsed = end.getTime() - start.getTime(); // elapsed time in milliseconds
// to test a function and get back its return
function printElapsedTime (fTest) {
	var nStartTime = Date.now(), 
            vReturn = fTest(),
            nEndTime = Date.now();

	alert("Elapsed time: " + String(nEndTime - nStartTime) + " milliseconds");
	return vReturn;
}

yourFunctionReturn = printElapsedTime(yourFunction);

Note: In browsers that support the Web Performance API's high-resolution time feature, window.performance.now can provide more reliable and precise measurements of elapsed time than Date.now.

Specifications

Specification Status Comment
ECMAScript 1st Edition. Implemented in JavaScript 1.1 Standard Initial definition.
ECMAScript Language Specification 5.1th Edition (ECMA-262) Standard  
ECMAScript Language Specification 6th Edition (ECMA-262) Draft  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

Reports of browser compatibility

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