Understanding the long-term recurrence of large earthquakes is fundamental to seismic hazard assessment, yet requires simulating complex physical processes beyond the scope of purely elastic rheologies. Viscoelastic relaxation is a key mechanism for postseismic deformation and long-term stress redistribution. We extend the open-source discontinuous Galerkin (DG) software tandem [1,6], originally developed for modeling Sequences of Earthquakes and Aseismic Slip (SEAS) with elastic rheology, to incorporate viscoelastic rheology using the standard linear solid (SLS) model [2]. We implement a viscoelastic stress formulation within YATeTo (Yet Another Tensor Toolbox) [3] and enable efficient time-dependent simulations of viscoelastic relaxation coupled with rate-and-state friction. While YATeTo generates highly optimized kernels for local DG operations, the requirement for solving time-dependent linear systems makes performance optimization an important aspect of the ongoing work. We first verify the viscoelastic kernel implementation against simple analytical solutions. The implementation is then verified against static viscoelastic benchmark problems [4][5], reproducing analytical stress relaxation and displacement evolutions. Finally, we apply this framework to rate-and-state SEAS simulations to quantify the effect of viscoelasticity on earthquake recurrence and postseismic deformation patterns, comparing them to purely elastic models. Our results demonstrate that volumetric DG-based SEAS models can capture key features of the earthquake cycle, highlighting the computational feasibility of using open-source software like tandem for scalable, viscoelastic earthquake cycle modeling.