diff --git a/rootdir/init.rc b/rootdir/init.rc
index e6f4f4a..a2b8f59 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -321,6 +321,9 @@
     # Set SELinux security contexts on upgrade or policy update.
     restorecon_recursive /data
 
+    # Check any timezone data in /data is newer than the copy in /system, delete if not.
+    exec u:r:tzdatacheck:s0 system system -- /system/bin/tzdatacheck /system/usr/share/zoneinfo /data/misc/zoneinfo
+
     # If there is no fs-post-data action in the init.<device>.rc file, you
     # must uncomment this line, otherwise encrypted filesystems
     # won't work.
diff --git a/tzdatacheck/Android.mk b/tzdatacheck/Android.mk
new file mode 100644
index 0000000..0e25f7d
--- /dev/null
+++ b/tzdatacheck/Android.mk
@@ -0,0 +1,21 @@
+LOCAL_PATH:= $(call my-dir)
+
+include $(CLEAR_VARS)
+
+# ========================================================
+# Executable
+# ========================================================
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES:= tzdatacheck.cpp
+LOCAL_MODULE := tzdatacheck
+LOCAL_SHARED_LIBRARIES := libbase libcutils liblog
+LOCAL_CFLAGS := -Werror
+include $(BUILD_EXECUTABLE)
+
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES:= tzdatacheck.cpp
+LOCAL_MODULE := tzdatacheck
+LOCAL_SHARED_LIBRARIES := libbase libcutils liblog
+LOCAL_CFLAGS := -Werror
+include $(BUILD_HOST_EXECUTABLE)
+
diff --git a/tzdatacheck/tzdatacheck.cpp b/tzdatacheck/tzdatacheck.cpp
new file mode 100644
index 0000000..31f7b55
--- /dev/null
+++ b/tzdatacheck/tzdatacheck.cpp
@@ -0,0 +1,236 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://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 <errno.h>
+#include <ftw.h>
+#include <libgen.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <iostream>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/logging.h"
+
+static const char* TZDATA_FILENAME = "/tzdata";
+// tzdata file header (as much as we need for the version):
+// byte[11] tzdata_version  -- e.g. "tzdata2012f"
+static const int TZ_HEADER_LENGTH = 11;
+
+static void usage() {
+    std::cerr << "Usage: tzdatacheck SYSTEM_TZ_DIR DATA_TZ_DIR\n"
+            "\n"
+            "Compares the headers of two tzdata files. If the one in SYSTEM_TZ_DIR is the\n"
+            "same or a higher version than the one in DATA_TZ_DIR the DATA_TZ_DIR is renamed\n"
+            "and then deleted.\n";
+    exit(1);
+}
+
+/*
+ * Opens a file and fills headerBytes with the first byteCount bytes from the file. It is a fatal
+ * error if the file is too small or cannot be opened. If the file does not exist false is returned.
+ * If the bytes were read successfully then true is returned.
+ */
+static bool readHeader(const std::string& tzDataFileName, char* headerBytes, size_t byteCount) {
+    FILE* tzDataFile = fopen(tzDataFileName.c_str(), "r");
+    if (tzDataFile == nullptr) {
+        if (errno == ENOENT) {
+            return false;
+        } else {
+            PLOG(FATAL) << "Error opening tzdata file " << tzDataFileName;
+        }
+    }
+    size_t bytesRead = fread(headerBytes, 1, byteCount, tzDataFile);
+    if (bytesRead != byteCount) {
+        LOG(FATAL) << tzDataFileName << " is too small. " << byteCount << " bytes required";
+    }
+    fclose(tzDataFile);
+    return true;
+}
+
+/* Checks the contents of headerBytes. It is a fatal error if it not a tzdata header. */
+static void checkValidHeader(const std::string& fileName, char* headerBytes) {
+    if (strncmp("tzdata", headerBytes, 6) != 0) {
+        LOG(FATAL) << fileName << " does not start with the expected bytes (tzdata)";
+    }
+}
+
+/* Return the parent directory of dirName. */
+static std::string getParentDir(const std::string& dirName) {
+    std::unique_ptr<char> mutable_dirname(strdup(dirName.c_str()));
+    return dirname(mutable_dirname.get());
+}
+
+/* Deletes a single file, symlink or directory. Called from nftw(). */
+static int deleteFn(const char* fpath, const struct stat*, int typeflag, struct FTW*) {
+    LOG(DEBUG) << "Inspecting " << fpath;
+    switch (typeflag) {
+    case FTW_F:
+    case FTW_SL:
+        LOG(DEBUG) << "Unlinking " << fpath;
+        if (unlink(fpath)) {
+            PLOG(WARNING) << "Failed to unlink file/symlink " << fpath;
+        }
+        break;
+    case FTW_D:
+    case FTW_DP:
+        LOG(DEBUG) << "Removing dir " << fpath;
+        if (rmdir(fpath)) {
+            PLOG(WARNING) << "Failed to remove dir " << fpath;
+        }
+        break;
+    default:
+        LOG(WARNING) << "Unsupported file type " << fpath << ": " << typeflag;
+        break;
+    }
+    return 0;
+}
+
+/*
+ * Deletes dirToDelete and returns true if it is successful in removing or moving the directory out
+ * of the way. If dirToDelete does not exist this function does nothing and returns true.
+ *
+ * During deletion, this function first renames the directory to a temporary name. If the temporary
+ * directory cannot be created, or the directory cannot be renamed, false is returned. After the
+ * rename, deletion of files and subdirs beneath the directory is performed on a "best effort"
+ * basis. Symlinks beneath the directory are not followed.
+ */
+static bool deleteDir(const std::string& dirToDelete) {
+    // Check whether the dir exists.
+    struct stat buf;
+    if (stat(dirToDelete.c_str(), &buf) == 0) {
+      if (!S_ISDIR(buf.st_mode)) {
+        LOG(WARNING) << dirToDelete << " is not a directory";
+        return false;
+      }
+    } else {
+      if (errno == ENOENT) {
+          PLOG(INFO) << "Directory does not exist: " << dirToDelete;
+          return true;
+      } else {
+          PLOG(WARNING) << "Unable to stat " << dirToDelete;
+          return false;
+      }
+    }
+
+    // First, rename dirToDelete.
+    std::string tempDirNameTemplate = getParentDir(dirToDelete);
+    tempDirNameTemplate += "/tempXXXXXX";
+
+    // Create an empty directory with the temporary name. For this we need a non-const char*.
+    std::vector<char> tempDirName(tempDirNameTemplate.length() + 1);
+    strcpy(&tempDirName[0], tempDirNameTemplate.c_str());
+    if (mkdtemp(&tempDirName[0]) == nullptr) {
+        PLOG(WARNING) << "Unable to create a temporary directory: " << tempDirNameTemplate;
+        return false;
+    }
+
+    // Rename dirToDelete to tempDirName.
+    int rc = rename(dirToDelete.c_str(), &tempDirName[0]);
+    if (rc == -1) {
+        PLOG(WARNING) << "Unable to rename directory from " << dirToDelete << " to "
+                << &tempDirName[0];
+        return false;
+    }
+
+    // Recursively delete contents of tempDirName.
+    rc = nftw(&tempDirName[0], deleteFn, 10 /* openFiles */,
+            FTW_DEPTH | FTW_MOUNT | FTW_PHYS);
+    if (rc == -1) {
+        LOG(INFO) << "Could not delete directory: " << &tempDirName[0];
+    }
+    return true;
+}
+
+/*
+ * After a platform update it is likely that timezone data found on the system partition will be
+ * newer than the version found in the data partition. This tool detects this case and removes the
+ * version in /data along with any update metadata.
+ *
+ * Note: This code is related to code in com.android.server.updates.TzDataInstallReceiver. The
+ * paths for the metadata and current timezone data must match.
+ *
+ * Typically on device the two args will be:
+ *   /system/usr/share/zoneinfo /data/misc/zoneinfo
+ *
+ * See usage() for usage notes.
+ */
+int main(int argc, char* argv[]) {
+    if (argc != 3) {
+        usage();
+    }
+
+    const char* systemZoneInfoDir = argv[1];
+    const char* dataZoneInfoDir = argv[2];
+
+    std::string dataCurrentDirName(dataZoneInfoDir);
+    dataCurrentDirName += "/current";
+    std::string dataTzDataFileName(dataCurrentDirName);
+    dataTzDataFileName += TZDATA_FILENAME;
+
+    std::vector<char> dataTzDataHeader;
+    dataTzDataHeader.reserve(TZ_HEADER_LENGTH);
+
+    bool dataFileExists = readHeader(dataTzDataFileName, dataTzDataHeader.data(), TZ_HEADER_LENGTH);
+    if (!dataFileExists) {
+        LOG(INFO) << "tzdata file " << dataTzDataFileName << " does not exist. No action required.";
+        return 0;
+    }
+    checkValidHeader(dataTzDataFileName, dataTzDataHeader.data());
+
+    std::string systemTzDataFileName(systemZoneInfoDir);
+    systemTzDataFileName += TZDATA_FILENAME;
+    std::vector<char> systemTzDataHeader;
+    systemTzDataHeader.reserve(TZ_HEADER_LENGTH);
+    bool systemFileExists =
+            readHeader(systemTzDataFileName, systemTzDataHeader.data(), TZ_HEADER_LENGTH);
+    if (!systemFileExists) {
+        LOG(FATAL) << systemTzDataFileName << " does not exist or could not be opened";
+    }
+    checkValidHeader(systemTzDataFileName, systemTzDataHeader.data());
+
+    if (strncmp(&systemTzDataHeader[0], &dataTzDataHeader[0], TZ_HEADER_LENGTH) < 0) {
+        LOG(INFO) << "tzdata file " << dataTzDataFileName << " is the newer than "
+                << systemTzDataFileName << ". No action required.";
+    } else {
+        // We have detected the case this tool is intended to prevent. Go fix it.
+        LOG(INFO) << "tzdata file " << dataTzDataFileName << " is the same as or older than "
+                << systemTzDataFileName << "; fixing...";
+
+        // Delete the update metadata
+        std::string dataUpdatesDirName(dataZoneInfoDir);
+        dataUpdatesDirName += "/updates";
+        LOG(INFO) << "Removing: " << dataUpdatesDirName;
+        bool deleted = deleteDir(dataUpdatesDirName);
+        if (!deleted) {
+            LOG(WARNING) << "Deletion of install metadata " << dataUpdatesDirName
+                    << " was not successful";
+        }
+
+        // Delete the TZ data
+        LOG(INFO) << "Removing: " << dataCurrentDirName;
+        deleted = deleteDir(dataCurrentDirName);
+        if (!deleted) {
+            LOG(WARNING) << "Deletion of tzdata " << dataCurrentDirName << " was not successful";
+        }
+    }
+
+    return 0;
+}