$dateFromParts

The $dateFromParts operator constructs a date from individual components such as year, month, day, hour, minute, second, and millisecond. This operator can be useful when dealing with data that stores date components separately.

Syntax

{ $dateFromParts: { year: <year>, month: <month>, day: <day>, hour: <hour>, minute: <minute>, second: <second>, millisecond: <millisecond>, timezone: <timezone> } }

Parameters

Parameter Description
year The year component of the date.
month The month component of the date.
day The day component of the date.
hour The hour component of the date.
minute The minute component of the date.
second The second component of the date.
millisecond The millisecond component of the date.
timezone Optional. A timezone specification.

Examples

Let's understand the usage with sample json from stores dataset.

{
  "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
  "name": "Relecloud | Toy Collection - North Jaylan",
  "location": {
    "lat": 2.0797,
    "lon": -94.4134
  },
  "staff": {
    "employeeCount": {
      "fullTime": 7,
      "partTime": 4
    }
  },
  "sales": {
    "salesByCategory": [
      {
        "categoryName": "Educational Toys",
        "totalSales": 3299
      }
    ],
    "revenue": 3299
  },
  "promotionEvents": [
    {
      "eventName": "Massive Markdown Mania",
      "promotionalDates": {
        "startDate": {
          "Year": 2024,
          "Month": 9,
          "Day": 21
        },
        "endDate": {
          "Year": 2024,
          "Month": 9,
          "Day": 29
        }
      },
      "discounts": [
        {
          "categoryName": "Remote Control Toys",
          "discountPercentage": 6
        },
        {
          "categoryName": "Building Sets",
          "discountPercentage": 21
        }
      ]
    }
  ],
  "company": "Relecloud",
  "city": "North Jaylan",
  "lastUpdated": {
    "$timestamp": {
      "t": 1733313006,
      "i": 1
    }
  },
  "storeOpeningDate": "2024-09-05T11:50:06.549Z"
}

Example 1: Constructing a start date

The aggregation query constructs precise startDate and endDate values from nested fields using $dateFromParts, then calculates the event duration in days. It helps standardize and analyze event timelines stored in fragmented date formats.

db.stores.aggregate([
  { 
    $match: { _id: "e6410bb3-843d-4fa6-8c70-7472925f6d0a" } 
  },
  { 
    $unwind: "$promotionEvents" 
  },
  {
    $project: {
      _id: 1,
      startDate: {
        $dateFromParts: {
          year: "$promotionEvents.promotionalDates.startDate.Year",
          month: "$promotionEvents.promotionalDates.startDate.Month",
          day: "$promotionEvents.promotionalDates.startDate.Day"
        }
      }
    }
  }
])

The query returns the _id and a computed startDate by extracting and assembling date parts from nested promotion data.

{
  "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
  "startDate": "2024-09-21T00:00:00.000Z"
}

Related content