nix-da/home/graphical/gammastep.nix

{
  services.gammastep = {
    enable = true;
    tray = true;
    temperature = {
      day = 6500;
      night = 4000;
    };
    dawnTime = "7:00-9:00";
    duskTime = "18:00-20:00";
  };
}