How to convert from string to date data type in MongoDB?

To convert from string to date data type in MongoDB, you can use the ISODate() function within a script that iterates through documents and updates them. This is useful when you have date fields stored as strings that need to be converted to proper date objects.

Syntax

db.collection.find().forEach(function(doc){
    doc.dateField = ISODate(doc.dateField);
    db.collection.save(doc);
});

Create Sample Data

Let us first create a collection with documents containing string date values ?

db.stringToDateDataTypeDemo.insertMany([
    {"CustomerName": "Carol", "ShippingDate": "2019-01-21"},
    {"CustomerName": "Bob", "ShippingDate": "2019-02-24"},
    {"CustomerName": "Chris", "ShippingDate": "2019-04-01"}
]);

{
    "acknowledged" : true,
    "insertedIds" : [
        ObjectId("5ca2071d66324ffac2a7dc60"),
        ObjectId("5ca2073566324ffac2a7dc61"),
        ObjectId("5ca2074266324ffac2a7dc62")
    ]
}

Display Original Data

db.stringToDateDataTypeDemo.find().pretty();

{
    "_id" : ObjectId("5ca2071d66324ffac2a7dc60"),
    "CustomerName" : "Carol",
    "ShippingDate" : "2019-01-21"
}
{
    "_id" : ObjectId("5ca2073566324ffac2a7dc61"),
    "CustomerName" : "Bob",
    "ShippingDate" : "2019-02-24"
}
{
    "_id" : ObjectId("5ca2074266324ffac2a7dc62"),
    "CustomerName" : "Chris",
    "ShippingDate" : "2019-04-01"
}

Convert String to Date

Use the following script to convert string dates to proper date objects ?

db.stringToDateDataTypeDemo.find().forEach(function(data){
    data.ShippingDate = ISODate(data.ShippingDate);
    db.stringToDateDataTypeDemo.save(data);
});

Verify Result

Display all documents to confirm the conversion ?

db.stringToDateDataTypeDemo.find().pretty();

{
    "_id" : ObjectId("5ca2071d66324ffac2a7dc60"),
    "CustomerName" : "Carol",
    "ShippingDate" : ISODate("2019-01-21T00:00:00Z")
}
{
    "_id" : ObjectId("5ca2073566324ffac2a7dc61"),
    "CustomerName" : "Bob",
    "ShippingDate" : ISODate("2019-02-24T00:00:00Z")
}
{
    "_id" : ObjectId("5ca2074266324ffac2a7dc62"),
    "CustomerName" : "Chris",
    "ShippingDate" : ISODate("2019-04-01T00:00:00Z")
}

Conclusion

The ISODate() function successfully converts string dates to MongoDB date objects. Use forEach() to iterate through documents and save() to persist the changes with proper date data types.