US Patent 9880523 Powerless time reference

According to an embodiment, a time reference device is provided. In the embodiment, the time reference device, includes a corrodible element, wherein a corrosion of the corrodible element advances with advancing time, and a sensor configured for providing a sensor signal, the sensor signal depending on a physical property of the corrodible element; wherein the physical property of the corrodible element changes with a corrosion of the corrodible element and the physical property of the corrodible element is at least one of an electrical property, a magnetic property, and an optical property. A barrier may be provided for defining a permeability for a corrosive substance to the corrodible element.