$dateFromString

Used to convert a date/time string to a date object. This operation can be useful when dealing with string representations of dates that need to be manipulated or queried as date objects.

Syntax

$dateFromString: { dateString: <string>, format: <string>, timezone: <string>, onError: <expression>, onNull: <expression> }

Parameters

dateStringstringrequired

The date/time string to convert to a date object.

formatstring

Optional. The date format specification of the dateString.

timezonestring

Optional. The timezone to use to format the date.

onErrorobject

Optional. The value to return if an error occurs while parsing the dateString.

onNullobject

Optional. The value to return if the dateString is null or missing.

Examples

Convert promotional event dates to ISO dates

This query constructs full ISO date strings from individual year, month, and day fields using $concat and converts them to startDate and endDate using $dateFromString.

Query:

db.stores.aggregate([
  {
    $match: { _id: "e6410bb3-843d-4fa6-8c70-7472925f6d0a" }
  },
  {
    $unwind: "$promotionEvents"
  },
  {
    $project: {
      eventName: "$promotionEvents.eventName",
      startDate: {
        $dateFromString: {
          dateString: {
            $concat: [
              { $toString: "$promotionEvents.promotionalDates.startDate.Year" },
              "-",
              {
                $cond: {
                  if: { $lt: ["$promotionEvents.promotionalDates.startDate.Month", 10] },
                  then: { $concat: ["0", { $toString: "$promotionEvents.promotionalDates.startDate.Month" }] },
                  else: { $toString: "$promotionEvents.promotionalDates.startDate.Month" }
                }
              },
              "-",
              {
                $cond: {
                  if: { $lt: ["$promotionEvents.promotionalDates.startDate.Day", 10] },
                  then: { $concat: ["0", { $toString: "$promotionEvents.promotionalDates.startDate.Day" }] },
                  else: { $toString: "$promotionEvents.promotionalDates.startDate.Day" }
                }
              }
            ]
          }
        }
      },
      endDate: {
        $dateFromString: {
          dateString: {
            $concat: [
              { $toString: "$promotionEvents.promotionalDates.endDate.Year" },
              "-",
              {
                $cond: {
                  if: { $lt: ["$promotionEvents.promotionalDates.endDate.Month", 10] },
                  then: { $concat: ["0", { $toString: "$promotionEvents.promotionalDates.endDate.Month" }] },
                  else: { $toString: "$promotionEvents.promotionalDates.endDate.Month" }
                }
              },
              "-",
              {
                $cond: {
                  if: { $lt: ["$promotionEvents.promotionalDates.endDate.Day", 10] },
                  then: { $concat: ["0", { $toString: "$promotionEvents.promotionalDates.endDate.Day" }] },
                  else: { $toString: "$promotionEvents.promotionalDates.endDate.Day" }
                }
              }
            ]
          }
        }
      }
    }
  }
])

Output:

[
  {
    "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
    "eventName": "Massive Markdown Mania",
    "startDate": "2024-09-21T00:00:00.000Z",
    "endDate": "2024-09-29T00:00:00.000Z"
  }
]