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$dateAdd

Adds a specified number of time units to a date. It's useful in scenarios where you need to calculate future dates based on a given date and a time interval.

Syntax

$dateAdd: { startDate: <expression>, unit: <string>, amount: <number>, timezone: <string> }

Parameters

startDateobjectrequired

The starting date for the addition operation.

unitstringrequired

The unit of time to add. Valid units include year, quarter, month, week, day, hour, minute, second, millisecond.

amountnumberrequired

The number of units to add.

timezonestring

Optional. The timezone to use for the operation.

Examples

Adding days to a date

This query projects eventName and computes a newEndDate by adding 7 days to a date constructed from nested year, month, and day fields.

Query:

db.stores.aggregate([
  { $match: { _id: "e6410bb3-843d-4fa6-8c70-7472925f6d0a" } },
  { $unwind: "$promotionEvents" },
  { $unwind: "$promotionEvents.promotionalDates" },
  {
    $project: {
      eventName: 1,
      newEndDate: {
        $dateAdd: {
          startDate: {
            $dateFromParts: {
              year: "$promotionEvents.promotionalDates.endDate.Year",
              month: "$promotionEvents.promotionalDates.endDate.Month",
              day: "$promotionEvents.promotionalDates.endDate.Day"
            }
          },
          unit: "day",
          amount: 7
        }
      }
    }
  }
])

Output:

[
   {
     "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
     "newEndDate": "2024-10-06T00:00:00.000Z"
   }
]

Adding months to a date

This aggregation query projects the eventName and calculates a newStartDate by adding 1 month to a reconstructed start date from nested promotion fields.

Query:

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

Output:

[
   {
     "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
     "eventName": "Massive Markdown Mania",
     "newStartDate": "2024-10-21T00:00:00.000Z"
   }
]

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