text: var ObjectId = require('mogoose').Schema.Types.ObjectId;
  
  function objectIdWithTimestamp(timestamp) {
    // Convert string date to Date object (otherwise assume timestamp is a date)
    if (typeof(timestamp) == 'string') {
      timestamp = new Date(timestamp);
    }
  
    // Convert date object to hex seconds since Unix epoch
    var hexSeconds = Math.floor(timestamp/1000).toString(16);
  
    // Create an ObjectId with that hex timestamp
    var constructedObjectId = ObjectId(hexSeconds + "0000000000000000");
  
    return constructedObjectId
  }
  
  exports.objectIdWithTimestamp = objectIdWithTimestamp;
  