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$isoDayOfWeek (aggregation)

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  • Definition
  • Behavior
  • Example
$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:

    { 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.

    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"
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.

A collection called birthdays contains the following documents:

db.birthdays.insertMany( [
{ _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.

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

The operation returns the following results:

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

Tip

See also:

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$isNumber