Exponential integrators are the most efficient class of methods for the time-stepping of stiff, semilinear, oscillatory PDEs such as the KdV equation. They solve the stiff, linear part of the PDE exactly. In the case of periodic boundary conditions, a Fourier spectral method can be used, so the linear part is diagonal and the methods can be applied straightforwardly. For other spatial discretizations, functions of the matrix exponential are required, which are susceptible to rounding errors. Several methods for evaluating these functions will be discussed.