Maxwell’s equations represented by differential operators describe the local dependence between both electric and magnetic fields in every location of space and time. This description responds to the field concept proposed by Michael Faraday and formalized by James Clerk Maxwell. The discretized version in the form of the finite-difference time-domain (FDTD) technique relies on a proposal of local computation of the respective differential operators making use of the central difference approximation of the second derivative of functions through the Taylor series expansion. This article introduces a novel time-symmetric “non-local” technique from the mathematical formalism of electromagnetic potentials in the wave equation and its physical interpretation in the Minkowski spacetime. In the proposed case study, the “non-local” proposal is 1643 faster than FDTD, i.e., more than three orders of magnitude, and it uses a time-step that is 4096 times greater than the Courant–Friedrichs–Lewy limit without encountering stability problems. New electromagnetic potentials are calculated from the previous and distant ones located at vertices of spatiotemporal regions called causal diamonds that tessellates spacetime without the need for computations inside them. We show that the performance gain is proportional to the size of the spacetime tessellations because the ratio “domain to boundary” increases as the domain extension does. Consequently, our novel “non-local” approach provides a reduction in computational complexity and a more comprehensible explanation of their fundamental physical aspects, without contradicting the principles of the successful classical field theory.