$hour (expression operator)

Definition

$hour

Returns the hour portion of a date as a number between 0 and 23.

The $hour expression has the following operator expression syntax:

{ $hour: <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

{ $hour: new Date("2016-01-01T12:00:00Z") }

{ $hour: { date: new Date("Jan 7, 2003Z") } }

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

{ $hour: ISODate("2017-10-19T00:00:00Z") }

{ $hour: {    date: ISODate("2017-10-19T00:00:00Z"),    timezone: "+0530"} }

{ $hour: "March 28, 1976" }

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

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

Example

Consider a sales collection with the following document:

 db.sales.insertOne(  {   "_id" : 1,   "item" : "abc",   "price" : 10,   "quantity" : 2,   "date" : ISODate("2014-01-01T08:15:39.736Z")  })

The following aggregation uses the $hour and other date expressions to break down the date field:

db.sales.aggregate(   [     {       $project:         {           year: { $year: "$date" },           month: { $month: "$date" },           day: { $dayOfMonth: "$date" },           hour: { $hour: "$date" },           minutes: { $minute: "$date" },           seconds: { $second: "$date" },           milliseconds: { $millisecond: "$date" },           dayOfYear: { $dayOfYear: "$date" },           dayOfWeek: { $dayOfWeek: "$date" }         }     }   ])

The operation returns the following result:

{  "_id" : 1,  "year" : 2014,  "month" : 1,  "day" : 1,  "hour" : 8,  "minutes" : 15,  "seconds" : 39,  "milliseconds" : 736,  "dayOfYear" : 1,  "dayOfWeek" : 4,  "week" : 0}