Mongoose Exception: can’t convert from BSON type EOO to Date

Updated: December 31, 2023 By: Guest Contributor Post a comment

Encountering data type conversion errors in Mongoose can be perplexing and frustrating. This tutorial dives into the ‘can’t convert from BSON type EOO to Date’ exception and offers solutions.

Understanding the Error

The error occurs when Mongoose tries to cast a value to a Date object, but encounters a ‘null’ or missing field instead. Let’s examine an example schema.

const mongoose = require('mongoose');
const { Schema } = mongoose;

const eventSchema = new Schema({
  eventDate: Date

Let’s Fix It

Basic Troubleshooting

Ensure that the date field is not null during insertion and conforms to the ISO date format accepted by JavaScript’s Date object.

const Event = mongoose.model('Event', eventSchema);

Event.create({ eventDate: new Date() })
  .then(event => console.log(event))
  .catch(err => console.error(err));

Dealing with Null Values

Provide default values or validate the data before insertion to handle null effectively.

  date => date != null,
  'eventDate cannot be null'

Advanced Data Handling

Implement pre-save hooks to manage complex date operations prior to saving a document.

eventSchema.pre('save', async function (next) {
  if (!this.eventDate) {
    this.eventDate = new Date();

Using Custom Casters

Create custom caster functions for handling ambiguous date inputs safely.

const safeDateCaster = val => val ? new Date(val) : null;


Inspecting Database Values

Perform regular database inspections to ensure that no corrupt or null date values exist that may trigger this exception.


This error has various sources but by validating data, providing default values and using custom casters, developers can ensure type safety in their Mongoose schemas.