$isoDayOfWeek (aggregation)¶

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Definition
Behavior
Example

Definition¶

$isoDayOfWeek¶

Returns the weekday number in ISO 8601 format, ranging from 1 (for Monday) to 7 (for Sunday).

The $isoDayOfWeek expression has the following operator expression syntax:

{ $isoDayOfWeek: <dateExpression> }

The argument can be:

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

A document with this format:

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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`	copy "America/New_York" "Europe/London" "GMT"
`UTC Offset`	copy +/-[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:

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{ "_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 each birthday field.

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

The operation returns the following results:

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