If we were not there, Cs or H atoms would still be the solution of Shredinger equation having the same energy levels thus oscillating with the same frequency. Earth would rotate with the same rate, etc. Remove humans - and NOTHING will change in the Universe. So, time is NOT human concept, it simply is a parameter of periodic processes. And as periodic processes are beyond human influence, so is time. Nothing to do with aliens, humans, animals, plants, etc.