Pendulum clock running rates can be adjusted by changing the length of the pendulums. Likewise the running rates of mechanical and electronic crystal clocks can be changed and adjusted. Can the running rate of an atomic clock also be adjusted? It doesn’t seem like there could be any way to change the quantum properties of the cesium 133 atoms, or whatever they are using now. So when they set the GPS clocks to run about 37 μs slow before launch, is that just some offset between what the cesium atoms are really doing and what the physics package is broadcasting to the outside world?