[welterde]

The author argues that only TAI would make sense to an alien civilization, but I don't think that's true at all. I think they miss the fact that it also is only defined within the reference frame of the Earth and also that it depends on many technically subtle aspects.

Especially if one only wants to communicate times between the civilizations, such as meet here at 13:00 in exactly three years from now. This is much easier to communicate based on rotation angles of the Earth than on a atomic time scale that would need to be transferred very precisely to be useful at all.