Methods, devices, and systems for synchronizing switching times of relays to a zero-crossing are described herein. One device includes a memory, and a processor configured to execute executable instructions stored in the memory to receive phase information of an alternating-current (AC) electric mains, determine, from the phase information, a zero-crossing of the phase of the AC electric mains, determine a reference time based on the zero-crossing for a number of relays corresponding to a number of relay controllers, and transmit the reference time to the number of relay controllers.