How to store/send Date types to MongoDB Model to avoid Validation Errors?

I got a Report model in MongoDB/Mongoose, most of them are String types, one is Boolean and two Date types with default to Date().now

date_posted: {
    type: Date,
    default: Date.now
},
date_lts: {
    type: Date,
    default: Date.now
},
approved: {
    type: Boolean,
    required: true
}

Now, from React Native, I'm doing a POST to my NodeJS app, where I use momentJS and new Date() for those fields.

 date_posted: new Date(),
 date_lts: moment(this.state.date).format(),

This is what the Server is receiving:

  date_posted: '2017-05-12T00:43:09.461Z',
  date_lts: '2017-05-11T00:00:00-03:00',

I'm thinking that since those are Strings, it might have some problems while validating those values.

So how should I build the POST HTTP request from React Native/Javascript for dates?

This would be the entire fetch() from my React Native app.

             var url = Constants.API_URL + '/reports/save';
             fetch(url, {
                method: 'POST',
                headers: {
                    'Accept': 'application/json',
                    'Content-Type': 'application/json'
                },
                body: JSON.stringify({
                    status: 'active',
                    image_url: this.state.imageUploadData.image_url,
                    image_name: this.state.imageUploadData.image_name,
                    date_posted: new Date(),
                    date_lts: moment(this.state.date).format(),
                    name: this.state.fullName,
                    country: this.props.countryName,
                    approved: false
                })
            })

Then in my app.js I got the following:

app.post('/api/reports/save', function(req, res) {
    var report = req.body;

    Report.addReport(report, function(err, report) {
        if(err) {
            throw err;
        }

        res.json(report);
    });
})

Then in my report model, i got this addReport() method which is like this:

module.exports.addReport = function(report, callback) {
    Report.create(report, callback);
}

In app.js server is throwing this error:

events.js:160
      throw er; // Unhandled 'error' event
      ^
ValidationError: Report validation failed
    at MongooseError.ValidationError (/Users/marian/Documents/dev/exampleapp/node_modules/mongoose/lib/error/validation.js:23:11)

via msqar