From e2b65c023983cd579e1f9eb050504fd5959ecb41 Mon Sep 17 00:00:00 2001
From: Jairo Llopis <yajo.sk8@gmail.com>
Date: Tue, 3 Dec 2024 09:30:45 +0100
Subject: [PATCH 1/2] nixos/tzupdate: make enabled module actually be enabled

Without this fix, when setting `services.tzupdate.enable = true`, the service would never run automatically.

Now, it's actually enabled in systemd and it actually gets executed.

Still, it could be improved with a timer as explained in https://github.com/NixOS/nixpkgs/issues/127984#issuecomment-2512059143, but this makes it at least work out of the box when rebooting the system.
---
 nixos/modules/services/misc/tzupdate.nix | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/nixos/modules/services/misc/tzupdate.nix b/nixos/modules/services/misc/tzupdate.nix
index 18fee37ddd1b..65a6f7d72098 100644
--- a/nixos/modules/services/misc/tzupdate.nix
+++ b/nixos/modules/services/misc/tzupdate.nix
@@ -26,11 +26,12 @@ in
     # zone, which is better than silently overriding it.
     time.timeZone = null;
 
-    # We provide a one-shot service which can be manually run. We could
-    # provide a service that runs on startup, but it's tricky to get
-    # a service to run after you have *internet* access.
+    # We provide a one-shot service that runs at startup once network
+    # interfaces are up, but we can’t ensure we actually have Internet access
+    # at that point. It can also be run manually with `systemctl start tzupdate`.
     systemd.services.tzupdate = {
       description = "tzupdate timezone update service";
+      wantedBy = [ "multi-user.target" ];
       wants = [ "network-online.target" ];
       after = [ "network-online.target" ];
       script = ''

From a6c31c856b44058079de808793f762aca38dadca Mon Sep 17 00:00:00 2001
From: Jairo Llopis <yajo.sk8@gmail.com>
Date: Mon, 16 Dec 2024 11:22:00 +0000
Subject: [PATCH 2/2] nixos/tzupdate: add timer and package options

---
 nixos/modules/services/misc/tzupdate.nix | 32 +++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/nixos/modules/services/misc/tzupdate.nix b/nixos/modules/services/misc/tzupdate.nix
index 65a6f7d72098..454b47620e11 100644
--- a/nixos/modules/services/misc/tzupdate.nix
+++ b/nixos/modules/services/misc/tzupdate.nix
@@ -18,6 +18,25 @@ in
         update the timezone.
       '';
     };
+
+    package = lib.mkPackageOption pkgs "tzupdate" { };
+
+    timer.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = ''
+        Enable the tzupdate timer to update the timezone automatically.
+      '';
+    };
+
+    timer.interval = lib.mkOption {
+      type = lib.types.str;
+      default = "hourly";
+      description = ''
+        The interval at which the tzupdate timer should run. See
+        {manpage}`systemd.time(7)` to understand the format.
+      '';
+    };
   };
 
   config = lib.mkIf cfg.enable {
@@ -35,7 +54,7 @@ in
       wants = [ "network-online.target" ];
       after = [ "network-online.target" ];
       script = ''
-        timezone="$(${lib.getExe pkgs.tzupdate} --print-only)"
+        timezone="$(${lib.getExe cfg.package} --print-only)"
         if [[ -n "$timezone" ]]; then
           echo "Setting timezone to '$timezone'"
           timedatectl set-timezone "$timezone"
@@ -46,6 +65,17 @@ in
         Type = "oneshot";
       };
     };
+
+    systemd.timers.tzupdate = {
+      enable = cfg.timer.enable;
+      interval = cfg.timer.interval;
+      timerConfig = {
+        OnStartupSec = "30s";
+        OnCalendar = cfg.timer.interval;
+        Persistent = true;
+      };
+      wantedBy = [ "timers.target" ];
+    };
   };
 
   meta.maintainers = with lib.maintainers; [ doronbehar ];