nixos-configuration/nix-os/locale.nix

{ ... }:

{
  config = {
    # Set your time zone.
    time.timeZone = "Europe/Warsaw";

    # Select internationalisation properties.
    i18n.defaultLocale = "en_US.UTF-8";

    i18n.extraLocaleSettings = {
      LC_ADDRESS = "pl_PL.UTF-8";
      LC_IDENTIFICATION = "pl_PL.UTF-8";
      LC_MEASUREMENT = "pl_PL.UTF-8";
      LC_MONETARY = "pl_PL.UTF-8";
      LC_NAME = "pl_PL.UTF-8";
      LC_NUMERIC = "pl_PL.UTF-8";
      LC_PAPER = "pl_PL.UTF-8";
      LC_TELEPHONE = "pl_PL.UTF-8";
      LC_TIME = "pl_PL.UTF-8";
    };

    # Configure keymap in X11
    services.xserver.xkb = {
      layout = "pl";
      variant = "";
    };

    # Configure console keymap
    console.keyMap = "pl2";
  };
}