$isoWeek (aggregation)

Definition

• $isoWeek

New in version 3.4.

Returns the week number in ISO 8601 format, ranging from 1 to53. Week numbers start at 1 with the week (Monday throughSunday) that contains the year’s first Thursday.

The $isoWeek expression has the followingoperator expression syntax:

{ $isoWeek: <dateExpression> }

Changed in version 3.6.

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

• A Date, aTimestamp,or an ObjectID.

• A document of the following form:

New in version 3.6.

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

FieldDescriptiondateThe date to which the operator is applied.<dateExpression> must be a valid expression that resolves to aDate, aTimestamp,or an ObjectID.timezoneOptional. The timezone of the operation result.<tzExpression> must be a valid expression that resolves to a string formatted as eitheran Olson Timezone Identifier or aUTC Offset.If no timezone is provided, the result is displayed in UTC.

FormatExamplesOlson 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" }

Note

$isoWeek cannot take a string as an argument.

Example

A collection called deliveries contains the following documents:

{ "_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 }

See also

• $isoDayOfWeek (aggregation)
• $isoWeekYear (aggregation)