Convert date parts to date in MongoDB

To convert separate date parts (year, month, day) into a complete date in MongoDB, use the $dateFromParts operator within an aggregation pipeline. This operator combines individual date components into a proper date object.

Syntax

db.collection.aggregate([
    {
        $project: {
            dateField: {
                $dateFromParts: {
                    year: "$yearField",
                    month: "$monthField", 
                    day: "$dayField"
                }
            }
        }
    }
]);

Sample Data

db.demo386.insertOne({
    details: { 
        Month: 02, 
        Day: 27, 
        Year: 2020 
    }
});

{ "acknowledged": true, "insertedId": ObjectId("...") }

db.demo386.find();

{ "_id": ObjectId("5e5bd9a222064be7ab44e7f7"), "details": { "Month": 2, "Day": 27, "Year": 2020 } }

Example: Convert Date Parts to Formatted Date String

db.demo386.aggregate([
    {
        $project: {
            _id: 0,
            DueDate: {
                $dateToString: {
                    format: "%m-%d-%Y",
                    date: {
                        $dateFromParts: {
                            year: "$details.Year",
                            month: "$details.Month",
                            day: "$details.Day"
                        }
                    }
                }
            }
        }
    }
]);

{ "DueDate": "02-27-2020" }

Key Points

• $dateFromParts creates a date object from separate year, month, and day values.
• Combine with $dateToString to format the resulting date as needed.
• The operator also accepts hour, minute, second, and millisecond for precise timestamps.

Conclusion

Use $dateFromParts in aggregation pipelines to construct complete dates from individual date components. This approach is essential when working with data where dates are stored as separate fields rather than proper date objects.