$isoWeek (expression operator)

Definition

$isoWeek

Returns the week number in ISO 8601 format, ranging from 1 to 53. Week numbers start at 1 with the week (Monday through Sunday) that contains the year's first Thursday.

The $isoWeek expression has the following operator expression syntax:

{ $isoWeek: <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

{ $isoWeek: { date: new Date("Jan 4, 2016") } }

{ $isoWeek: new Date("2016-01-01") }

{ $isoWeek: {    date: new Date("August 14, 2011"),    timezone: "America/Chicago"} }

{ $isoWeek: ISODate("1998-11-02T00:00:00Z") }

{ $isoWeek: {    date: ISODate("1998-11-02T00:00:00Z"),    timezone: "-0500"} }

{ $isoWeek: "March 28, 1976" }

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

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

Example

A collection called deliveries contains the following documents:

db.deliveries.insertMany( [   { _id: 1, date: ISODate("2006-10-24T00:00:00Z"), city: "Boston" },   { _id: 2, date: ISODate("2011-08-18T00:00:00Z"), city: "Detroit" }] )

The following operation returns the week number for each date field.

db.deliveries.aggregate( [  {    $project: {      _id: 0,      city: "$city",      weekNumber: { $isoWeek: "$date" }    }  }] )

The operation returns the following results:

[   { city: "Boston", weekNumber: 43 },   { city: "Detroit", weekNumber: 33 }]