old_contents: // Example model
  
  var mongoose = require('mongoose'),
    Schema = mongoose.Schema;
  
  var ArticleSchema = new Schema({
    title: String,
    url: String,
    text: String
  });
  
  ArticleSchema.virtual('date')
    .get(function(){
      return this._id.getTimestamp();
    });
  
  mongoose.model('Article', ArticleSchema);
  
new_contents: // Example model
  var mongoose = require('mongoose'),
    Schema = mongoose.Schema;
  
  var ArticleSchema = new Schema({
    title: String,
    url: String,
    text: String
  });
  
  ArticleSchema.virtual('date')
    .get(function(){
      return this._id.getTimestamp();
    });
  
  mongoose.model('Article', ArticleSchema);
  
subject: fix white space