Date
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.
Syntax
new Date(); new Date(<var>value</var>); new Date(<var>dateString</var>); new Date(<var>year</var>, <var>month</var>[, <var>day</var>[, <var>hour</var>[, <var>minutes</var>[, <var>seconds</var>[, <var>milliseconds</var>]]]]]);
Note: 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.
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
.
Note: Where Date
is called as a constructor with more than one argument, the specifed arguments represent local time. If UTC is desired, use new Date(
with the same arguments.Date.UTC(...)
)
value
- Integer value representing the number of milliseconds since 1 January 1970 00:00:00 UTC (Unix Epoch; but consider that most Unix time stamp functions count in seconds).
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).Note: parsing of date strings with the
Date
constructor (andDate.parse
, they are equivalent) is strongly discouraged due to browser differences and inconsistencies. 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
- Optional. Integer value representing the day of the month.
hour
- Optional. Integer value representing the hour of the day.
minute
- Optional. Integer value representing the minute segment of a time.
second
- Optional. Integer value representing the second segment of a time.
millisecond
- Optional. 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 thenew
operator) will return a string representing the current date and time.
Properties
Date.prototype
- Allows the addition of properties to a JavaScript
Date
object. Date.length
- The value of
Date.length
is 7. This is the number of arguments handled by the constructor.
Methods
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, UTC.
Note: Parsing of strings with
Date.parse
is strongly discouraged due to browser differences and inconsistencies. 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.
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.
Date.prototype 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
usingtoISOString()
. Intended for use byJSON.stringify()
. Date.prototype.toGMTString()
- Returns a string representing the
Date
based on the GMT (UT) time zone. UsetoUTCString()
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 theObject.prototype.toSource()
method. Date.prototype.toString()
- Returns a string representing the specified
Date
object. Overrides theObject.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 theObject.prototype.valueOf()
method.
Examples
Several ways to create a Date
object
The following examples show several ways to create JavaScript dates:
Note: parsing of date strings with the Date
constructor (and Date.parse
, they are equivalent) is strongly discouraged due to browser differences and inconsistencies.
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);
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)
Calculating elapsed time
The following examples show how to determine the elapsed time between two JavaScript dates in millisconds.
Due to the differing lengths of days (due to daylight saving changeover), months and years, expressing elapsed time in units greater than hours, minutes and seconds requires addressing a number of issues and should be thoroughly researched before being attempted.
// 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(); console.log('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, Performance.now()
can provide more reliable and precise measurements of elapsed time than Date.now()
.
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2017 Draft (ECMA-262) The definition of 'Date' in that specification. |
Draft | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Date' in that specification. |
Standard | |
ECMAScript 5.1 (ECMA-262) The definition of 'Date' in that specification. |
Standard | |
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.1. |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) [1] | (Yes) [1] | (Yes) [2] | (Yes) [1] | (Yes) [1] |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
[1] Some browsers can have issues when parsing dates: 3/14/2012 blog from danvk Comparing FF/IE/Chrome on Parsing Date Strings
[2] ISO8601 Date Format is not supported in Internet Explorer 8, and other version can have issues when parsing dates
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/javascript/reference/global_objects/date