$dateTrunc - Amazon DocumentDB
Example (MongoDB Shell)Code examples
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$dateTrunc

New from version 8.0

Not supported by Elastic cluster.

The $dateTrunc aggregation operator in Amazon DocumentDB truncates a date to a specified unit.

Parameters

  • date: A date expression that resolves to a date or timestamp.

  • unit: A string that specifies the time unit for the subtrahend expression. Supported units are year, quarter, month, week, day, hour, minute, second, and millisecond.

Example (MongoDB Shell)

The following example demonstrates how to use the $dateTrunc operator to truncate a date to to the hour.

Create sample documents

db.events.insertMany([
  {
    eventName: "Event 1",
    eventTime: ISODate("2025-04-01T12:15:00Z")
  },
  {
    eventName: "Event 2",
    eventTime: ISODate("2025-08-15T14:33:22Z")
  },
]);

Query example

db.events.aggregate([
  {
    $project: {
      eventName: 1,
      eventTime: 1,
      truncatedToHour: {
        $dateTrunc: {
          date: "$eventTime",
          unit: "hour"
        }
      }
    }
  }
]);

Output

[
  {
    _id: ObjectId('6924a258d66dcae121d29515'),
    eventName: 'Event 1',
    eventTime: ISODate('2025-04-01T12:15:00.000Z'),
    truncatedToHour: ISODate('2025-04-01T12:00:00.000Z')
  },
  {
    _id: ObjectId('6924a258d66dcae121d29516'),
    eventName: 'Event 2',
    eventTime: ISODate('2025-08-15T14:33:22.000Z'),
    truncatedToHour: ISODate('2025-08-15T14:00:00.000Z')
  }
]

Code examples

To view a code example for using the $dateTrunc command, choose the tab for the language that you want to use:

Node.js
const { MongoClient } = require('mongodb');

async function example() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const events = db.collection('events');
  
  const result = await events.aggregate([
    {
      $project: {
        eventName: 1,
        eventTime: 1,
        truncatedToHour: {
          $dateTrunc: {
            date: "$eventTime",
            unit: "hour"
          }
        }
      }
    }
  ]).toArray();
  
  console.log(result);
  client.close();
}

example();
Python
from pymongo import MongoClient

def example():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    events = db['events']
    
    result = list(events.aggregate([
        {
            "$project": {
                "eventName": 1,
                "eventTime": 1,
                "truncatedToHour": {
                    "$dateTrunc": {
                        "date": "$eventTime",
                        "unit": "hour"
                    }
                }
            }
        }
    ]))
    
    print(result)
    client.close()

example()