pb
Wormhole mouths (and I won't entertain any other method of time travel) would be gravitationally and inertially bound to their system like a grain of rice, or moon, or whatthefuckever and using them would negate the need to plot some type of 4D trajectory relative to the location of earth, the sun, the milky way, the local cluster, supercluster, etc.
just sayin, I'm not ready to get into a big theoretical physics thing right now because turbomigraine