$isoDayOfWeek (aggregation)

$isoDayOfWeek (aggregation)

Definition

$isoDayOfWeek

New in version 3.4.

Returns the weekday number in ISO 8601 format, ranging from1 (for Monday) to 7 (for Sunday).

The $isoDayOfWeek expression has the followingoperator expression syntax:

{ $isoDayOfWeek: <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

Example	Result
{ $isoDayOfWeek: new Date("2016-01-01") }	5
{ $isoDayOfWeek: { date: new Date("Jan 7, 2003") } }	2
{ $isoDayOfWeek: { date: new Date("August 14, 2011"), timezone: "America/Chicago"} }	7
{ $isoDayOfWeek: ISODate("1998-11-07T00:00:00Z") }	6
{ $isoDayOfWeek: { date: ISODate("1998-11-07T00:00:00Z"), timezone: "-0400"} }	5
{ $isoDayOfWeek: "March 28, 1976" }	`error`
{ $isoDayOfWeek: Date("2016-01-01") }	`error`
{ $isoDayOfWeek: "2009-04-09" }	`error`

Note

$isoDayOfWeek cannot take a string as an argument.

Example

A collection called birthdays contains the following documents:

{ "_id" : 1, "name" : "Betty", "birthday" : ISODate("1993-09-21T00:00:00Z") }
{ "_id" : 2, "name" : "Veronica", "birthday" : ISODate("1981-11-07T00:00:00Z") }

The following operation returns the weekday number for eachbirthday field.

db.dates.aggregate( [
  {
    $project: {
      _id: 0,
      name: "$name",
      dayOfWeek: { $isoDayOfWeek: "$birthday" }
    }
  }
] )

The operation returns the following results:

{ "name" : "Betty", "dayOfWeek" : 2 }
{ "name" : "Veronica", "dayOfWeek" : 6 }