$isoWeekYear (expression operator)

Definition

$isoWeekYear

Returns the year number in ISO 8601 format. The year starts with the Monday of week 1 and ends with the Sunday of the last week.

The $isoWeekYear expression has the following operator expression syntax:

{ $isoWeekYear: <dateExpression> }

The argument can be:

• An expression that resolves to a Date, a Timestamp, or an ObjectID.

• A document with this format:

  { date: <dateExpression>, timezone: <tzExpression> }

  Field	Description
  date	The date to which the operator is applied. <dateExpression> must be a valid expression that resolves to a Date, a Timestamp, or an ObjectID.
  timezone	Optional. The timezone of the operation result. <tzExpression> must be a valid expression that resolves to a string formatted as either an Olson Timezone Identifier or a UTC Offset. If no timezone is provided, the result is in UTC. Olson Timezone Identifier: "America/New_York""Europe/London""GMT" UTC Offset: +/-[hh]:[mm], e.g. "+04:45"+/-[hh][mm], e.g. "-0530"+/-[hh], e.g. "+03"

Behavior

{ $isoWeekYear: new Date("2015-05-26") }

{ $isoWeekYear: { date: new Date("Jan 7, 2003") } }

{ $isoWeekYear: ISODate("2017-01-02T00:00:00Z") }

{ $isoWeekYear: {    date: ISODate("2017-01-02T00:00:00Z"),    timezone: "-0500"} }

{ $isoWeekYear: {    date: new Date("April 08, 2024"),    timezone: "America/Chicago"} }

{ $isoWeekYear: "March 28, 1976" }

{ $isoWeekYear: Date("2016-01-01") }

{ $isoWeekYear: "2009-04-09" }

Example

A collection called anniversaries contains the following documents:

{ "_id" : 1, "date" : ISODate("2016-01-01T00:00:00Z") }{ "_id" : 2, "date" : ISODate("2016-01-04T00:00:00Z") }{ "_id" : 3, "date" : ISODate("2015-01-01T00:00:00Z") }{ "_id" : 4, "date" : ISODate("2014-04-21T00:00:00Z") }

The following operation returns the year number in ISO 8601 format for each date field.

db.anniversaries.aggregate( [  {    $project: {      yearNumber: { $isoWeekYear: "$date" }    }  }] )

The operation returns the following results:

{ "_id" : 1, "yearNumber" : 2015 }{ "_id" : 2, "yearNumber" : 2016 }{ "_id" : 3, "yearNumber" : 2015 }{ "_id" : 4, "yearNumber" : 2014 }