Abstract: In relativistic heavy-ion collisions, magnetic fields as strong as 10¹⁸~10¹⁹ G can be produced by near-light-speed nuclear impacts. We systematically investigate the spatiotemporal evolution of the electromagnetic (EM) fields using three theoretical approaches: solving Maxwell’s equations, estimating the vacuum EM fields, and applying the Liénard–Wiechert potential. Calculations are carried out for Au+Au, Zr+Zr, Ru+Ru, and Pb+Pb collisions across the GeV–TeV energy regions, including predictions for Pb+Pb collisions under future Large Hadron Collider upgrade scenarios (FCC and HE-LHC). Our results show that although the temporal evolution of the EM fields differs among the three methods, their intensities all decay rapidly with increasing \sqrts_\rmNN^ . The strong magnetic field is mainly localized in the overlapping region of the participating nucleons, while the strong electric field gradually concentrates on both sides of this region over time.