Relative time dependence as gauge freedom and bilocal models of hadrons

The shift of relative time variable is introduced as a gauge transformation of bilocal field operator. The corresponding gauge invariant free bilocal Lagrangian theory is formulated. The subsidiary condition which eliminates the relative time appears as a guage invariance condition for bilocal field operator. As an example the bilocal field describing covariant three dimensional oscillator model of hadrons is quantized. (Auth.)