feat(timezone): opt-in automatic, location-following timezone

nomarchy.system.autoTimezone (off by default): geoclue + automatic-
timezoned drive /etc/localtime from your location, so travelling to
another zone updates the Waybar clock on its own.

Menu-driven, in-flake state (the night-light / keyboard philosophy):
the flag is settings.autoTimezone in theme-state.json (git-tracked); a
System-menu entry toggles it. Because it's a SYSTEM service — not a user
unit it can start/stop instantly like night-light — the toggle
(nomarchy-autotimezone, run in a terminal) writes the flag --no-switch
then drives `sudo nixos-rebuild` (bakes the service + the time.timeZone
override) plus `home-manager switch` (the Waybar-refresh watcher); both
sides read the one flag.

- modules/nixos/timezone.nix: parses settings.autoTimezone from
  nomarchy.system.stateFile (like Plymouth), gates geoclue2 +
  automatic-timezoned, and mkForce-nulls time.timeZone — automatic-
  timezoned sets it null at normal priority, which collides with the
  installer's static value (a hard eval error), so force wins and
  reverts cleanly when disabled. Ships the nomarchy-autotimezone toggle.
- modules/home/timezone.nix: a tiny user service watching timedate1's
  change signal that reloads Waybar (SIGUSR2) on a real zone change, so
  the clock follows live (Waybar captures the zone at construction).
  Gated on the same flag via nomarchy.settings.autoTimezone.
- rofi menu: "Auto timezone (on/off)" in the System submenu.
- option + template example + ROADMAP entry; theme.nix seeds the flag.

Eval-verified on (geoclue+daemon on, tz forced null over a static
installer value, watcher present) and off (static tz intact, nothing
extra); home + system both build green. Needs an on-hardware check
(geoclue detection + the SIGUSR2 clock refresh aren't CI-testable).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/default.nix

@@ -18,6 +18,7 @@
     ./yazi.nix      # flagship TUI file manager, themed + plugins
     ./osd.nix       # swayosd volume/brightness OSD, themed
     ./nightlight.nix # scheduled blue-light filter (hyprsunset), opt-in
+    ./timezone.nix  # keep the Waybar clock in step with auto-timezone changes
     ./updates.nix   # passive update-awareness indicator + notification, opt-in
     ./shell.nix     # zsh + starship + bat/eza/zoxide, themed
     ./keys.nix      # gpg-agent (fronts SSH) + pinentry-qt

modules/home/rofi.nix

@@ -324,6 +324,14 @@ ${themeRows}
           && exec nomarchy-nightlight toggle
         notify-send "Night light" "Not available (nomarchy.nightlight off?)."; exit 0 ;;
 
+      autotimezone)
+        # Toggle automatic timezone detection (geoclue + automatic-timezoned).
+        # A SYSTEM service, so flipping it writes the in-flake flag and runs a
+        # system rebuild (sudo) + a home switch — in a terminal, like Snapshots.
+        command -v nomarchy-autotimezone >/dev/null 2>&1 \
+          || { notify-send "Auto timezone" "Unavailable on this machine."; exit 0; }
+        exec ${cfg.terminal} -e nomarchy-autotimezone toggle ;;
+
       snapshot)
         # btrfs-assistant 2.2 segfaults on 26.05 (libbtrfsutil ABI), so launch
         # the keyboard-driven snapper browser instead: a terminal running it
@@ -374,6 +382,10 @@ ${themeRows}
           then row "Night light (on)"  weather-clear-night
           else row "Night light (off)" weather-clear-night
           fi
+          if [ "$(nomarchy-theme-sync get settings.autoTimezone 2>/dev/null)" = true ]
+          then row "Auto timezone (on)"  preferences-system-time
+          else row "Auto timezone (off)" preferences-system-time
+          fi
           command -v nomarchy-snapshots >/dev/null 2>&1 && row "Snapshots" timeshift
           if [ -e "''${bats[0]}" ] && command -v powerprofilesctl >/dev/null 2>&1; then
             row "Power profile" preferences-system-power
@@ -388,6 +400,7 @@ ${themeRows}
           *Printers*)         exec "$0" printers ;;
           *"Do Not Disturb"*) exec "$0" dnd ;;
           *"Night light"*)    exec "$0" nightlight ;;
+          *"Auto timezone"*)  exec "$0" autotimezone ;;
           *Snapshots*)        exec "$0" snapshot ;;
           *"Power profile"*)  exec "$0" power-profile ;;
         esac ;;
@@ -414,7 +427,7 @@ ${themeRows}
         esac ;;
 
       *)
-        echo "usage: nomarchy-menu [tools|system|power|power-profile|theme|clipboard|calc|files|emoji|web|network|bluetooth|audio|printers|capture|keybinds|ask|dnd|nightlight|snapshot]" >&2
+        echo "usage: nomarchy-menu [tools|system|power|power-profile|theme|clipboard|calc|files|emoji|web|network|bluetooth|audio|printers|capture|keybinds|ask|dnd|nightlight|autotimezone|snapshot]" >&2
         exit 64 ;;
     esac
   '';

modules/home/theme.nix

@@ -66,6 +66,10 @@ let
     settings = {
       nightlight = { installed = false; on = true; };
       keyboard.devices = { };
+      # Automatic timezone detection (nomarchy.system.autoTimezone): a system
+      # service, but the flag lives here so both sides read one source — the
+      # home side gates the Waybar-refresh watcher (timezone.nix) on it.
+      autoTimezone = false;
     };
   };
 

modules/home/timezone.nix

@@ -0,0 +1,44 @@
+# Auto-timezone, home side: keep the Waybar clock in step with the system
+# timezone. Waybar's clock module captures the zone once at construction, so a
+# runtime timezone change (automatic-timezoned, nomarchy.system.autoTimezone)
+# would NOT show until a relogin. A tiny watcher subscribes to timedate1's
+# change signal and reloads Waybar (SIGUSR2 = the same reload theme-sync uses),
+# so the clock follows your location live. Also catches a manual
+# `timedatectl set-timezone`.
+#
+# Gated on the same in-flake flag the system side reads (settings.autoTimezone,
+# exposed via nomarchy.settings) — so it only runs when the feature is on. The
+# menu toggle (nomarchy-autotimezone) rebuilds both sides off that one flag.
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.nomarchy;
+  enabled = cfg.waybar.enable && (cfg.settings.autoTimezone or false);
+
+  tzWatch = pkgs.writeShellScript "nomarchy-tz-watch" ''
+    last=$(${pkgs.systemd}/bin/timedatectl show -p Timezone --value 2>/dev/null || true)
+    ${pkgs.dbus}/bin/dbus-monitor --system \
+      "type='signal',interface='org.freedesktop.DBus.Properties',path='/org/freedesktop/timedate1',member='PropertiesChanged'" \
+      2>/dev/null |
+    while read -r _; do
+      cur=$(${pkgs.systemd}/bin/timedatectl show -p Timezone --value 2>/dev/null || true)
+      [ "$cur" = "$last" ] && continue
+      last=$cur
+      ${pkgs.procps}/bin/pkill -SIGUSR2 -x waybar 2>/dev/null || true
+    done
+  '';
+in
+{
+  systemd.user.services.nomarchy-tz-watch = lib.mkIf enabled {
+    Unit = {
+      Description = "Reload Waybar on timezone change (auto-timezone)";
+      PartOf = [ "graphical-session.target" ];
+      After = [ "graphical-session.target" ];
+    };
+    Service = {
+      ExecStart = "${tzWatch}";
+      Restart = "on-failure";
+    };
+    Install.WantedBy = [ "graphical-session.target" ];
+  };
+}

modules/nixos/default.nix

@@ -22,7 +22,7 @@ let
   '';
 in
 {
-  imports = [ ./options.nix ./plymouth.nix ./file-manager.nix ./power.nix ./services.nix ./hardware.nix ];
+  imports = [ ./options.nix ./plymouth.nix ./file-manager.nix ./power.nix ./services.nix ./hardware.nix ./timezone.nix ];
 
   config = {
     # The safe half of distro branding: distroName flows into

modules/nixos/options.nix

@@ -46,6 +46,16 @@
     audio.enable = lib.mkEnableOption "the Pipewire audio stack" // { default = true; };
     bluetooth.enable = lib.mkEnableOption "Bluetooth support with blueman" // { default = true; };
 
+    autoTimezone.enable = lib.mkEnableOption ''
+      automatic timezone detection (geoclue + automatic-timezoned): the
+      system timezone — and so the Waybar clock — follows your location, so
+      travelling to another zone updates the time on its own. Off by default
+      (it's a location service and needs the network); toggle it from the
+      System menu, which lands the choice in the in-flake state file. Enabling
+      it unsets the static time.timeZone for you (a runtime timezone needs
+      /etc/localtime writable), so the menu toggle drives a system rebuild''
+      // { default = false; };
+
     snapper.enable = lib.mkEnableOption ''
       hourly/daily BTRFS timeline snapshots of / via snapper, plus the
       `nixos-rebuild-snap` pre-rebuild-snapshot helper. No-op unless the

modules/nixos/timezone.nix

@@ -0,0 +1,87 @@
+# Automatic timezone detection (opt-in) — the system timezone, and so the
+# Waybar clock, follows your location, so travelling to another zone updates
+# the time on its own. Geoclue feeds `automatic-timezoned`, which drives
+# /etc/localtime at runtime.
+#
+# In-flake state, menu-driven (the keyboard/night-light philosophy): the on/off
+# flag lives in the same theme-state.json under `settings.autoTimezone`
+# (git-tracked, reproducible), written by the System-menu toggle
+# (nomarchy-autotimezone). Because this is a SYSTEM service — not a user unit it
+# can start/stop instantly like night-light — the toggle drives a system rebuild
+# (plus a home switch for the Waybar-refresh watcher in timezone.nix home-side).
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.nomarchy.system;
+
+  # Read the same state file the rest of the system side uses (Plymouth too),
+  # wired by lib.mkFlake. The flag defaults off when the file is absent/sparse.
+  state =
+    if cfg.stateFile != null
+    then builtins.fromJSON (builtins.readFile cfg.stateFile)
+    else { };
+  stateEnabled = (state.settings or { }).autoTimezone or false;
+
+  sync = lib.getExe pkgs.nomarchy-theme-sync;
+
+  # Menu/CLI toggle. Runs as the normal user (it owns the flake checkout +
+  # writes the state); sudos only the system switch, like sys-update. Writes
+  # the in-flake flag, then rebuilds: the system rebuild bakes the service +
+  # the time.timeZone override, the home switch installs/removes the Waybar
+  # refresh watcher — both read the same flag we just wrote.
+  nomarchy-autotimezone = pkgs.writeShellScriptBin "nomarchy-autotimezone" ''
+    set -e
+    if [ "$(id -u)" -eq 0 ]; then
+      echo "nomarchy-autotimezone: run as your normal user (it sudos the rebuild itself)" >&2
+      exit 1
+    fi
+    flake="''${NOMARCHY_PATH:-$HOME/.nomarchy}"
+
+    cur=$(${sync} get settings.autoTimezone 2>/dev/null) || cur=false
+    case "''${1:-toggle}" in
+      on)        new=true ;;
+      off)       new=false ;;
+      toggle)    case "$cur" in true|True) new=false ;; *) new=true ;; esac ;;
+      status)    echo "$cur"; exit 0 ;;
+      *) echo "usage: nomarchy-autotimezone [toggle|on|off|status]" >&2; exit 64 ;;
+    esac
+
+    ${sync} --quiet set settings.autoTimezone "$new" --no-switch
+
+    if [ "$new" = true ]; then
+      notify-send "Auto timezone" "Enabling — rebuilding the system…" 2>/dev/null || true
+    else
+      notify-send "Auto timezone" "Disabling — rebuilding the system…" 2>/dev/null || true
+    fi
+
+    sudo nixos-rebuild switch --flake "$flake#default"
+    home-manager switch --flake "$flake"
+
+    if [ "$new" = true ]; then
+      notify-send "Auto timezone on" "The clock now follows your location." 2>/dev/null || true
+    else
+      notify-send "Auto timezone off" "Back to the fixed timezone in system.nix." 2>/dev/null || true
+    fi
+  '';
+in
+{
+  config = lib.mkMerge [
+    {
+      # Shipped unconditionally so the menu can enable the feature even while
+      # it's off. Track the in-flake flag; mkDefault so a hand-set
+      # nomarchy.system.autoTimezone.enable in system.nix still wins.
+      environment.systemPackages = [ nomarchy-autotimezone ];
+      nomarchy.system.autoTimezone.enable = lib.mkDefault stateEnabled;
+    }
+
+    (lib.mkIf cfg.autoTimezone.enable {
+      services.geoclue2.enable = true;
+      services.automatic-timezoned.enable = true;
+      # A runtime timezone needs /etc/localtime writable. automatic-timezoned
+      # sets time.timeZone = null itself, but the installer writes a static
+      # value at normal priority, which would collide (a hard eval error) —
+      # mkForce null overrides both and resolves cleanly.
+      time.timeZone = lib.mkForce null;
+    })
+  ];
+}