645.js

var mongoose = require('mongoose');
mongoose.connect('localhost', 'testing_645');


var schema = new mongoose.Schema({
    dtStart: Date
});
var Org = new mongoose.Schema({ events: [schema] });

var A = mongoose.model('A', Org);

mongoose.connection.on('open', function () {
  A.create({ events: [{ dtStart: new Date }] }, function (err, d) {
    if (err) return console.error(err.stack||err);
    console.error(d);

    A.find({ 'events.dtStart': { $gte: Date.now() }}, function (err, docs) {
      if (err) return console.error(err.stack||err);
      console.error(docs);

      mongoose.connection.db.dropDatabase(function () {
        mongoose.connection.close();
      });
    });
  })
});