diff --git a/download-iana-files.py b/download-iana-files.py
new file mode 100755
index 0000000..bcf551f
--- /dev/null
+++ b/download-iana-files.py
@@ -0,0 +1,156 @@
+#!/usr/bin/python -B
+
+# Copyright 2017 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.
+
+"""Downloads the latest IANA time zone files."""
+
+import argparse
+import ftplib
+import os
+import shutil
+import subprocess
+import sys
+
+sys.path.append('%s/external/icu/tools' % os.environ.get('ANDROID_BUILD_TOP'))
+import i18nutil
+import tzdatautil
+
+# Calculate the paths that are referred to by multiple functions.
+android_build_top = i18nutil.GetAndroidRootOrDie()
+iana_data_dir = os.path.realpath('%s/system/timezone/input_data/iana' % android_build_top)
+iana_tools_dir = os.path.realpath('%s/system/timezone/input_tools/iana' % android_build_top)
+
+def FtpRetrieveFile(ftp, filename):
+  ftp.retrbinary('RETR %s' % filename, open(filename, 'wb').write)
+
+
+def CheckSignature(data_filename, signature_filename):
+  """Checks the signature of a file."""
+  print 'Verifying signature of %s using %s...' % (data_filename, signature_filename)
+  try:
+    subprocess.check_call(['gpg', '--trusted-key=ED97E90E62AA7E34', '--verify',
+                          signature_filename, data_filename])
+  except subprocess.CalledProcessError as err:
+    print 'Unable to verify signature'
+    print '\n\n******'
+    print 'If this fails for you, you probably need to import Paul Eggert''s public key:'
+    print '  gpg --receive-keys ED97E90E62AA7E34'
+    print '******\n\n'
+    raise
+
+
+def FindLatestRemoteTar(ftp, file_prefix):
+  iana_tar_filenames = []
+
+  for filename in ftp.nlst():
+    if "/" in filename:
+      print "FTP server returned bogus file name"
+      sys.exit(1)
+
+    if filename.startswith(file_prefix) and filename.endswith('.tar.gz'):
+      iana_tar_filenames.append(filename)
+
+  iana_tar_filenames.sort(reverse=True)
+
+  if len(iana_tar_filenames) == 0:
+    print 'No files found'
+    sys.exit(1)
+
+  return iana_tar_filenames[0]
+
+
+def DownloadAndReplaceLocalFiles(file_prefixes, ftp, local_dir):
+  output_files = []
+
+  for file_prefix in file_prefixes:
+    latest_iana_tar_filename = FindLatestRemoteTar(ftp, file_prefix)
+    local_iana_tar_file = tzdatautil.GetIanaTarFile(local_dir, file_prefix)
+    if local_iana_tar_file:
+      local_iana_tar_filename = os.path.basename(local_iana_tar_file)
+      if latest_iana_tar_filename <= local_iana_tar_filename:
+        print('Latest remote file for %s is called %s and is older or the same as'
+              ' current local file %s'
+              % (local_dir, latest_iana_tar_filename, local_iana_tar_filename))
+        continue
+
+    print 'Found new %s* file for %s: %s' % (file_prefix, local_dir, latest_iana_tar_filename)
+    i18nutil.SwitchToNewTemporaryDirectory()
+
+    print 'Downloading file %s...' % latest_iana_tar_filename
+    FtpRetrieveFile(ftp, latest_iana_tar_filename)
+
+    signature_filename = '%s.asc' % latest_iana_tar_filename
+    print 'Downloading signature %s...' % signature_filename
+    FtpRetrieveFile(ftp, signature_filename)
+
+    CheckSignature(latest_iana_tar_filename, signature_filename)
+
+    new_local_iana_tar_file = '%s/%s' % (local_dir, latest_iana_tar_filename)
+    shutil.copyfile(latest_iana_tar_filename, new_local_iana_tar_file)
+    new_local_signature_file = '%s/%s' % (local_dir, signature_filename)
+    shutil.copyfile(signature_filename, new_local_signature_file)
+
+    output_files.append(new_local_iana_tar_file)
+    output_files.append(new_local_signature_file)
+
+    # Delete the existing local IANA tar file, if there is one.
+    if local_iana_tar_file:
+      os.remove(local_iana_tar_file)
+
+    local_signature_file = '%s.asc' % local_iana_tar_file
+    if os.path.exists(local_signature_file):
+      os.remove(local_signature_file)
+
+  return output_files
+
+# Run from any directory after having run source/envsetup.sh / lunch
+# See http://www.iana.org/time-zones/ for more about the source of this data.
+def main():
+  parser = argparse.ArgumentParser(description=('Update IANA files from upstream'))
+  parser.add_argument('--notools', help='Skip tools files', action='store_true')
+  parser.add_argument('--nodata', help='Skip data files', action='store_true')
+  args = parser.parse_args()
+  if args.notools and args.nodata:
+    parser.error("Nothing to do")
+    sys.exit(1)
+
+  print 'Looking for new IANA files...'
+
+  ftp = ftplib.FTP('ftp.iana.org')
+  ftp.login()
+  ftp.cwd('tz/releases')
+
+  output_files = []
+  if not args.notools:
+    # The tools and data files are kept separate to make the updates independent.
+    # This means we duplicate the tzdata20xx file (once in the tools dir, once
+    # in the data dir) but the contents of the data tar appear to be needed for
+    # the zic build.
+    new_files = DownloadAndReplaceLocalFiles(['tzdata20', 'tzcode20'], ftp, iana_tools_dir)
+    output_files += new_files
+  if not args.nodata:
+    new_files = DownloadAndReplaceLocalFiles(['tzdata20'], ftp, iana_data_dir)
+    output_files += new_files
+
+  if len(output_files) == 0:
+    print 'No files updated'
+  else:
+    print 'New files:'
+    for output_file in output_files:
+      print '  %s' % output_file
+
+
+if __name__ == '__main__':
+  main()