This package is useful for end-devices which do not have access to other accurate time source. An end-device using LoRaWAN 1.1 or above SHOULD use DeviceTimeReq MAC command instead of this package. ClassB end-devices have a more efficient way of synchronizing their clock, the classB network beacon. They SHOULD NOT use this package and directly use the beacon time information. End-devices with an accurate external clock source (e.g.: GPS) SHOULD use that clock source instead.