Date() constructor - JavaScript 编辑

Creates a JavaScript Date instance that represents a single moment in time in a platform-independent format. Date objects contain a Number that represents milliseconds since 1 January 1970 UTC.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

new Date()
new Date(value)
new Date(dateString)
new Date(year, monthIndex [, day [, hours [, minutes [, seconds [, milliseconds]]]]])

Note: The only correct way to instantiate a new Date object is by using the new operator. If you call the Date object directly, such as now = Date(), the returned value is a string rather than a Date object.

Parameters

There are four basic forms for the Date() constructor:

1. No parameters

   When no parameters are provided, the newly-created Date object represents the current date and time as of the time of instantiation.

2. Time value or timestamp number

   value

   An integer value representing the number of milliseconds since January 1, 1970, 00:00:00 UTC (the ECMAScript epoch, equivalent to the UNIX epoch), with leap seconds ignored. Keep in mind that most UNIX Timestamp functions are only accurate to the nearest second.

3. Timestamp string

   dateString

   A string value representing a date, specified in a format recognized by the Date.parse() method. (These formats are IETF-compliant RFC 2822 timestamps, and also strings in a version of ISO8601.)

   Note: Parsing of date strings with the Date constructor (and Date.parse(), which works the same way) is strongly discouraged due to browser differences and inconsistencies.

   • Support for RFC 2822 format strings is by convention only.
   • Support for ISO 8601 formats differs in that date-only strings (e.g. "1970-01-01") are treated as UTC, not local.

4. Individual date and time component values

   Given at least a year and month, this form of Date() returns a Date object whose component values (year, month, day, hour, minute, second, and millisecond) all come from the following parameters. Any missing fields are given the lowest possible value (1 for day and 0 for every other component).

   year

   Integer value representing the year.

   Values from 0 to 99 map to the years 1900 to 1999. All other values are the actual year. See the example.

   monthIndex

   Integer value representing the month, beginning with 0 for January to 11 for December.

   day Optional

   Integer value representing the day of the month. The default is 1.

   hours Optional

   Integer value representing the hour of the day. The default is 0 (midnight).

   minutes Optional

   Integer value representing the minute segment of a time. The default is 0 minutes past the hour.

   seconds Optional

   Integer value representing the second segment of a time. The default is 0 seconds past the minute.

   milliseconds Optional

   Integer value representing the millisecond segment of a time. The default is 0 milliseconds past the second.

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.

let today = new Date()
let birthday = new Date('December 17, 1995 03:24:00')
let birthday = new Date('1995-12-17T03:24:00')
let birthday = new Date(1995, 11, 17)            // the month is 0-indexed
let birthday = new Date(1995, 11, 17, 3, 24, 0)

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'Date' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• Date