From e22b99d3342b0ca6fae0f9631f4d69737dac0773 Mon Sep 17 00:00:00 2001
From: Mitsu <tech.mitsu.yuki@gmail.com>
Date: Sun, 21 Dec 2025 13:31:26 +0900
Subject: [PATCH 1/3] refactor: extract tzVersion from tzdata URL

---
 scripts/tzgen/main.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/scripts/tzgen/main.go b/scripts/tzgen/main.go
index 51b2ba5..dcb5062 100644
--- a/scripts/tzgen/main.go
+++ b/scripts/tzgen/main.go
@@ -16,7 +16,10 @@ import (
 	"strings"
 )
 
-const tzdataURL = "https://data.iana.org/time-zones/releases/tzdata2025b.tar.gz"
+const (
+	tzVersion = "2025b"
+	tzdataURL = "https://data.iana.org/time-zones/releases/tzdata" + tzVersion + ".tar.gz"
+)
 
 func main() {
 	if err := run(context.Background()); err != nil {

From 8de0073fad5a451733136e9b860313914b600a63 Mon Sep 17 00:00:00 2001
From: Mitsu <tech.mitsu.yuki@gmail.com>
Date: Sun, 21 Dec 2025 13:33:46 +0900
Subject: [PATCH 2/3] ci: add tzdata update workflow

---
 .github/workflows/tzdata-update.yml | 51 +++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 .github/workflows/tzdata-update.yml

diff --git a/.github/workflows/tzdata-update.yml b/.github/workflows/tzdata-update.yml
new file mode 100644
index 0000000..996319a
--- /dev/null
+++ b/.github/workflows/tzdata-update.yml
@@ -0,0 +1,51 @@
+name: tzdata update
+on:
+  schedule:
+    - cron: "0 23 * * *"
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v4
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - name: Fetch latest tzcode version
+        run: |
+          set -euo pipefail
+          workdir=$(mktemp -d)
+          wget -O "$workdir/tzcode-latest.tar.gz" https://www.iana.org/time-zones/repository/tzcode-latest.tar.gz
+          tar -xzf "$workdir/tzcode-latest.tar.gz" -C "$workdir"
+
+          version_file=$(find "$workdir" -maxdepth 2 -type f -name version | head -n 1)
+          if [ -z "$version_file" ]; then
+            echo "version file not found in tzcode-latest.tar.gz" >&2
+            exit 1
+          fi
+
+          latest_version=$(tr -d ' \n' < "$version_file")
+          current_version=$(grep -E 'tzVersion' scripts/tzgen/main.go | sed -E 's/.*"([^"]+)".*/\1/' | head -n 1)
+
+          echo "current=$current_version latest=$latest_version"
+          if [ "$latest_version" = "$current_version" ]; then
+            echo "tzdata is already up to date"
+            exit 0
+          fi
+
+          sed -i.bak -E 's/tzVersion = ".*"/tzVersion = "'"$latest_version"'"/' scripts/tzgen/main.go
+          rm -f scripts/tzgen/main.go.bak
+          gofmt -w scripts/tzgen/main.go
+          go run scripts/tzgen/main.go
+
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add scripts/tzgen/main.go tz
+          git commit -m "Update tzdata to ${latest_version}"
+          git push

From 160d879b4c751fafd2e1cc06271354275901d1a3 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Mon, 22 Dec 2025 23:24:07 +0000
Subject: [PATCH 3/3] Update tzdata to 2025c

---
 scripts/tzgen/main.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/tzgen/main.go b/scripts/tzgen/main.go
index dcb5062..a3737e8 100644
--- a/scripts/tzgen/main.go
+++ b/scripts/tzgen/main.go
@@ -17,7 +17,7 @@ import (
 )
 
 const (
-	tzVersion = "2025b"
+	tzVersion = "2025c"
 	tzdataURL = "https://data.iana.org/time-zones/releases/tzdata" + tzVersion + ".tar.gz"
 )