For photon time passes only for itself (because relative to itself it is not moving). Any interaction with photon (i.e. what we call "observing"), happens with

For photon time passes only for itself (because relative to itself it is not moving). Any interaction with photon (i.e. what we call "observing"), happens with t=0 from perspective of something that collided with photon, and normal time from the perspective of photon (which happens to be spatial distance from perspective of something that collided with photon).