diff --git a/eng/testing/tests.mobile.targets b/eng/testing/tests.mobile.targets
index 039b0d9a39b3c..0b8bad5cb3aad 100644
--- a/eng/testing/tests.mobile.targets
+++ b/eng/testing/tests.mobile.targets
@@ -155,7 +155,7 @@
              AssemblyFile="$(CreateCreateWasmBundlesAssemblyPath)" />
   <Target Condition="'$(TargetOS)' == 'Browser'" Name="LoadTimeZone" >
     <PropertyGroup>
-      <TimeZoneDataVersion>2020a</TimeZoneDataVersion>
+      <TimeZoneDataVersion>2020d</TimeZoneDataVersion>
     </PropertyGroup>
     <DownloadTimeZoneData
       InputDirectory="$(BundleDir)obj/data/input"
diff --git a/src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs b/src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs
index c659446475eba..20716ad604774 100644
--- a/src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs
+++ b/src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs
@@ -2287,6 +2287,50 @@ public static void TestNameWithInvariantCulture()
 
         }
 
+        [Theory]
+        [PlatformSpecific(TestPlatforms.Browser)]
+        [InlineData("America/Buenos_Aires", "America/Argentina/Buenos_Aires")]
+        [InlineData("America/Catamarca", "America/Argentina/Catamarca")]
+        [InlineData("America/Cordoba", "America/Argentina/Cordoba")]
+        [InlineData("America/Jujuy", "America/Argentina/Jujuy")]
+        [InlineData("America/Mendoza", "America/Argentina/Mendoza")]
+        [InlineData("America/Indianapolis", "America/Indiana/Indianapolis")]
+        public static void TestTimeZoneIdBackwardCompatibility(string oldId, string currentId)
+        {
+            TimeZoneInfo oldtz = TimeZoneInfo.FindSystemTimeZoneById(oldId);
+            TimeZoneInfo currenttz = TimeZoneInfo.FindSystemTimeZoneById(currentId);
+
+            Assert.Equal(oldtz.StandardName, currenttz.StandardName);
+            Assert.Equal(oldtz.DisplayName, currenttz.DisplayName);
+        }
+
+        [Theory]
+        [PlatformSpecific(TestPlatforms.Browser)]
+        [InlineData("America/Buenos_Aires")]
+        [InlineData("America/Catamarca")]
+        [InlineData("America/Cordoba")]
+        [InlineData("America/Jujuy")]
+        [InlineData("America/Mendoza")]
+        [InlineData("America/Indianapolis")]
+        public static void ChangeLocalTimeZone(string id) 
+        {
+            string originalTZ = Environment.GetEnvironmentVariable("TZ");
+            try {
+                TimeZoneInfo.ClearCachedData();
+                Environment.SetEnvironmentVariable("TZ", id);
+
+                TimeZoneInfo localtz = TimeZoneInfo.Local;
+                TimeZoneInfo tz = TimeZoneInfo.FindSystemTimeZoneById(id);
+
+                Assert.Equal(tz.StandardName, localtz.StandardName);
+                Assert.Equal(tz.DisplayName, localtz.DisplayName); 
+            }
+            finally {
+                TimeZoneInfo.ClearCachedData();
+                Environment.SetEnvironmentVariable("TZ", originalTZ);
+            }
+        }
+
         private static bool IsEnglishUILanguageAndRemoteExecutorSupported => (CultureInfo.CurrentUICulture.Name == "en" || CultureInfo.CurrentUICulture.Name.StartsWith("en-", StringComparison.Ordinal)) && RemoteExecutor.IsSupported;
 
         private static void VerifyConvertException<TException>(DateTimeOffset inputTime, string destinationTimeZoneId) where TException : Exception
diff --git a/src/mono/wasm/wasm.targets b/src/mono/wasm/wasm.targets
index 92b1f37809e6a..13b9e9f23c329 100644
--- a/src/mono/wasm/wasm.targets
+++ b/src/mono/wasm/wasm.targets
@@ -40,7 +40,7 @@
     <DownloadTimeZoneData
       InputDirectory="$(ArtifactsObjDir)wasm/data/input"
       OutputDirectory="$(ArtifactsObjDir)wasm/data/output"
-      Version="2020a" />
+      Version="2020d" />
   </Target>
 
   <UsingTask TaskName="CreateWasmBundle" AssemblyFile="$([MSBuild]::NormalizePath('$(ArtifactsBinDir)', 'CreateWasmBundle', 'Debug', '$(NetCoreAppCurrent)', 'publish', 'CreateWasmBundle.dll'))"/>
diff --git a/tools-local/tasks/mobile.tasks/CreateWasmBundle/DownloadTimeZoneData.cs b/tools-local/tasks/mobile.tasks/CreateWasmBundle/DownloadTimeZoneData.cs
index 0d3501dfbb2a2..36d8430154672 100644
--- a/tools-local/tasks/mobile.tasks/CreateWasmBundle/DownloadTimeZoneData.cs
+++ b/tools-local/tasks/mobile.tasks/CreateWasmBundle/DownloadTimeZoneData.cs
@@ -25,7 +25,7 @@ public class DownloadTimeZoneData : Task
 
     private void DownloadTimeZoneDataSource() 
     {
-        List<string> files = new List<string>() {"africa", "antarctica", "asia", "australasia", "etcetera", "europe", "northamerica", "southamerica", "zone1970.tab"};
+        List<string> files = new List<string>() {"africa", "antarctica", "asia", "australasia", "etcetera", "europe", "northamerica", "southamerica", "zone1970.tab", "backward"};
         using (var client = new WebClient())
         {
             Console.WriteLine("Downloading TimeZone data files");