lib: support setting process.env.TZ on windows

Fixes: #4230
Signed-off-by: James M Snell <[email protected]>

Author: jasnell

src/node.cc

@@ -937,6 +937,14 @@ int InitializeNodeWithArgs(std::vector<std::string>* argv,
     return 9;
   }
   per_process::metadata.versions.InitializeIntlVersions();
+
+# ifndef __POSIX__
+  std::string tz;
+  if (credentials::SafeGetenv("TZ", &tz) && !tz.empty()) {
+    i18n::SetDefaultTimeZone(tz.c_str());
+  }
+# endif
+
 #endif
 
   NativeModuleEnv::InitializeCodeCache();

src/node_env_var.cc

@@ -2,6 +2,7 @@
 #include "env-inl.h"
 #include "node_errors.h"
 #include "node_external_reference.h"
+#include "node_i18n.h"
 #include "node_process.h"
 
 #include <time.h>  // tzset(), _tzset()
@@ -69,15 +70,29 @@ std::shared_ptr<KVStore> system_environment = std::make_shared<RealEnvStore>();
 }  // namespace per_process
 
 template <typename T>
-void DateTimeConfigurationChangeNotification(Isolate* isolate, const T& key) {
+void DateTimeConfigurationChangeNotification(Isolate* isolate, const T& key, const char* val = nullptr) {
   if (key.length() == 2 && key[0] == 'T' && key[1] == 'Z') {
 #ifdef __POSIX__
     tzset();
+    isolate->DateTimeConfigurationChangeNotification(
+        Isolate::TimeZoneDetection::kRedetect);
 #else
     _tzset();
+
+# if defined(NODE_HAVE_I18N_SUPPORT)
+    isolate->DateTimeConfigurationChangeNotification(
+        Isolate::TimeZoneDetection::kSkip);
+
+    // On windows, the TZ environment is not supported out of the box.
+    // By default, v8 will only be able to detect the system configured
+    // timezone. This supports using the TZ environment variable to set
+    // the default timezone instead.
+    if (val != nullptr) i18n::SetDefaultTimeZone(val);
+# else
+    isolate->DateTimeConfigurationChangeNotification(
+        Isolate::TimeZoneDetection::kRedetect);
+# endif
 #endif
-    auto constexpr time_zone_detection = Isolate::TimeZoneDetection::kRedetect;
-    isolate->DateTimeConfigurationChangeNotification(time_zone_detection);
   }
 }
 
@@ -128,7 +143,7 @@ void RealEnvStore::Set(Isolate* isolate,
   if (key.length() > 0 && key[0] == '=') return;
 #endif
   uv_os_setenv(*key, *val);
-  DateTimeConfigurationChangeNotification(isolate, key);
+  DateTimeConfigurationChangeNotification(isolate, key, *val);
 }
 
 int32_t RealEnvStore::Query(const char* key) const {

src/node_i18n.cc

@@ -542,6 +542,14 @@ bool InitializeICUDirectory(const std::string& path) {
   return status == U_ZERO_ERROR;
 }
 
+void SetDefaultTimeZone(const char* tzid) {
+  UChar lbl[255];
+  UErrorCode status = U_ZERO_ERROR;
+  u_charsToUChars(tzid, lbl, strlen(tzid) + 1);
+  ucal_setDefaultTimeZone(lbl, &status);
+  CHECK(U_SUCCESS(status));
+}
+
 int32_t ToUnicode(MaybeStackBuffer<char>* buf,
                   const char* input,
                   size_t length) {

src/node_i18n.h

@@ -40,6 +40,8 @@ namespace i18n {
 
 bool InitializeICUDirectory(const std::string& path);
 
+void SetDefaultTimeZone(const char* tzid);
+
 enum idna_mode {
   // Default mode for maximum compatibility.
   IDNA_DEFAULT,

test/parallel/test-datetime-change-notify.js

@@ -0,0 +1,13 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+
+process.env.TZ = 'Etc/UTC';
+assert.match(new Date().toString(), /GMT\+0000/);
+
+process.env.TZ = 'America/New_York';
+assert.match(new Date().toString(), /Eastern (Standard|Daylight) Time/);
+
+process.env.TZ = 'America/Los_Angeles';
+assert.match(new Date().toString(), /Pacific (Standard|Daylight) Time/);