We study a posteriori error estimates of Crank–Nicolson–Galerkin type methods for time discretizations of reaction-diffusion equations with delay. In view of the weak discontinuous property of the solutions to delay equations, a posteriori error estimates are of utmost important in numerically solving this class of equations. To derive optimal order a posteriori error estimates, delay-dependent reconstructions for both the Crank–Nicolson–Galerkin method and the Crank–Nicolson method are introduced. By using these continuous, piecewise-quadratic time reconstruction...
