Import of CCTZ from GitHub.

PiperOrigin-RevId: 937377865
Change-Id: I5c7a2bd29db0124f177d6c841a00c254c7346df9

absl/time/internal/cctz/BUILD.bazel

diff --git a/absl/time/internal/cctz/BUILD.bazel b/absl/time/internal/cctz/BUILD.bazel
index e7e2ee0..3b47877 100644
--- a/absl/time/internal/cctz/BUILD.bazel
+++ b/absl/time/internal/cctz/BUILD.bazel
@@ -160,6 +160,23 @@
     ],
 )
 
+cc_test(
+    name = "time_zone_name_win_test",
+    size = "small",
+    srcs = select({
+        "@platforms//os:windows": ["src/time_zone_name_win_test.cc"],
+        "//conditions:default": [],
+    }),
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":time_zone",
+        "//absl/base:config",
+        "@googletest//:gtest",
+        "@googletest//:gtest_main",
+    ],
+)
+
 ### benchmarks
 
 cc_test(

absl/time/internal/cctz/src/time_zone_name_win.cc

diff --git a/absl/time/internal/cctz/src/time_zone_name_win.cc b/absl/time/internal/cctz/src/time_zone_name_win.cc
index 07aa8fa..7a1236f 100644
--- a/absl/time/internal/cctz/src/time_zone_name_win.cc
+++ b/absl/time/internal/cctz/src/time_zone_name_win.cc
@@ -118,7 +118,7 @@
   const auto ucal_getTimeZoneIDForWindowsIDRef =
       AsProcAddress<ucal_getTimeZoneIDForWindowsID_func>(
           icu_dll, "ucal_getTimeZoneIDForWindowsID");
-  if (ucal_getTimeZoneIDForWindowsIDRef != nullptr) {
+  if (ucal_getTimeZoneIDForWindowsIDRef == nullptr) {
     g_unavailable.store(true, std::memory_order_relaxed);
     return nullptr;
   }

absl/time/internal/cctz/src/time_zone_name_win_test.cc

diff --git a/absl/time/internal/cctz/src/time_zone_name_win_test.cc b/absl/time/internal/cctz/src/time_zone_name_win_test.cc
new file mode 100644
index 0000000..260c972
--- /dev/null
+++ b/absl/time/internal/cctz/src/time_zone_name_win_test.cc
@@ -0,0 +1,49 @@
+// Copyright 2026 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+#include "absl/time/internal/cctz/src/time_zone_name_win.h"
+
+#include <windows.h>
+
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/time/internal/cctz/include/cctz/time_zone.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+namespace cctz {
+
+TEST(TimeZoneNameWin, GetWindowsLocalTimeZone) {
+  // On Windows 10 1809+ (where icu.dll is available in System32),
+  // GetWindowsLocalTimeZone() should return a valid IANA time zone name.
+  // Note that LOAD_LIBRARY_SEARCH_SYSTEM32 is not sufficient to reliably load
+  // "icu.dll" in the production code, but it should be OK for testing purposes.
+  HMODULE icu_dll =
+      ::LoadLibraryExW(L"icu.dll", nullptr, LOAD_LIBRARY_SEARCH_SYSTEM32);
+  const std::string tz = GetWindowsLocalTimeZone();
+  if (icu_dll != nullptr) {
+    EXPECT_FALSE(tz.empty());
+    ::FreeLibrary(icu_dll);
+  } else {
+    EXPECT_TRUE(tz.empty());
+  }
+}
+
+}  // namespace cctz
+}  // namespace time_internal
+ABSL_NAMESPACE_END
+}  // namespace absl