$isoWeekYear (aggregation)¶

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Definition
Behavior
Example

Definition¶

$isoWeekYear¶

New in version 3.4.

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:

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{ $isoWeekYear: <dateExpression> }

Changed in version 3.6.

The argument must be a valid expression that resolves to one of the following:

A Date, a Timestamp, or an ObjectID.

A document of the following form:

New in version 3.6.

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{ 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 displayed in UTC.

`Format`	`Examples`
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¶

Example	Result
{ $isoWeekYear: new Date("2015-05-26") }	2015
{ $isoWeekYear: { date: new Date("Jan 7, 2003") } }	2003
{ $isoWeekYear: ISODate("2017-01-02T00:00:00Z") }	2017
{ $isoWeekYear: { date: ISODate("2017-01-02T00:00:00Z"), timezone: "-0500" } }	2016
{ $isoWeekYear: { date: new Date("April 08, 2024"), timezone: "America/Chicago" } }	2024
{ $isoWeekYear: "March 28, 1976" }	`error`
{ $isoWeekYear: Date("2016-01-01") }	`error`
{ $isoWeekYear: "2009-04-09" }	`error`

Note

$isoWeekYear cannot take a string as an argument.

Example¶

A collection called anniversaries contains the following documents:

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{ "_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.

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

The operation returns the following results:

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