  We demonstrate that the Finite-Time-Path Field Theory is an adequate tool for
calculating neutrino oscillations. We apply this theory using a mass-mixing
Lagrangian which involves the correct Dirac spin and chirality structure and a
Pontecorvo-Maki-Nakagawa-Sakata (PMNS)-like mixing matrix. The model is exactly
solvable. The Dyson-Schwinger equations transform propagators of the input free
(massless) flavor neutrinos into a linear combination of oscillating (massive)
neutrinos. The results are consistent with the predictions of the PMNS matrix
while allowing for extrapolation to early times.
