convertir el timestamp en una fecha

app/controllers/readings_controller.rb

@@ -57,6 +57,8 @@ class ReadingsController < ActionController::API
   def sensor_params(sensor)
     sensor.permit(:timestamp, :type, :value, :unit, :error).tap do |p|
       p[:local_type] = p.delete :type
+      p[:timestamp] = Time.at p[:timestamp]
+    rescue TypeError
     end
   end
 end