Spectral deferred correction (SDC) methods are attractive for
reaction-diffusion equations as they provide a lot of freedom for adaptive
control of various algorithmic parameters. Unfortunately, their convergence
rate is only satisfactory on equidistant time grids. In this talk we take a
purely linear algebra view on SDC methods and introduce customized
nonstandard
DIRK sweeps that recover fast convergence even on nonuniform time grids
such
as Radau points. The methods are designed on the Dahlquist test equation
and
their numerical properties are studied on some nonautonomous examples.