  We develop an electromagnetic symplectic structure on the space-time manifold
by defining a Poisson bracket in terms of an invertible electromagnetic tensor
F_{\mu\nu}. Moreover, we define electromagnetic symplectic diffeomorphisms by
imposing a special condition on the electromagnetic tensor. This condition
implies a special constraint on the Levi-Civita tensor. Then, we express
geometrically the electromagnetic duality by defing a dual local coordinates
system.
