diff --git a/libc/tools/zoneinfo/update-tzdata.py b/libc/tools/zoneinfo/update-tzdata.py
new file mode 100755
index 0000000..ffcdf54
--- /dev/null
+++ b/libc/tools/zoneinfo/update-tzdata.py
@@ -0,0 +1,179 @@
+#!/usr/bin/python
+
+"""Updates the tzdata file."""
+
+import ftplib
+import httplib
+import os
+import re
+import subprocess
+import sys
+import tarfile
+import tempfile
+
+# Find the bionic directory, searching upward from this script.
+bionic_libc_tools_zoneinfo_dir = os.path.realpath(os.path.dirname(sys.argv[0]))
+bionic_libc_tools_dir = os.path.dirname(bionic_libc_tools_zoneinfo_dir)
+bionic_libc_dir = os.path.dirname(bionic_libc_tools_dir)
+bionic_dir = os.path.dirname(bionic_libc_dir)
+bionic_libc_zoneinfo_dir = '%s/libc/zoneinfo' % bionic_dir
+
+if not os.path.isdir(bionic_libc_tools_zoneinfo_dir):
+  print "Couldn't find bionic/libc/tools/zoneinfo!"
+  sys.exit(1)
+if not os.path.isdir(bionic_libc_zoneinfo_dir):
+  print "Couldn't find bionic/libc/zoneinfo!"
+  sys.exit(1)
+
+print 'Found bionic in %s...' % bionic_dir
+
+
+regions = ['africa', 'antarctica', 'asia', 'australasia', 'backward',
+           'etcetera', 'europe', 'northamerica', 'southamerica']
+
+
+def GetCurrentTzDataVersion():
+  return open('%s/tzdata' % bionic_libc_zoneinfo_dir).read().split('\x00', 1)[0]
+
+
+def WriteSetupFile():
+  """Writes the list of zones that ZoneCompactor should process."""
+  links = []
+  zones = []
+  for region in regions:
+    for line in open('extracted/%s' % region):
+      fields = line.split()
+      if fields:
+        if fields[0] == 'Link':
+          links.append('%s %s %s\n' % (fields[0], fields[1], fields[2]))
+          zones.append(fields[2])
+        elif fields[0] == 'Zone':
+          zones.append(fields[1])
+  zones.sort()
+
+  setup = open('setup', 'w')
+  for link in links:
+    setup.write(link)
+  for zone in zones:
+    setup.write('%s\n' % zone)
+  setup.close()
+
+
+def SwitchToNewTemporaryDirectory():
+  tmp_dir = tempfile.mkdtemp('-tzdata')
+  os.chdir(tmp_dir)
+  print 'Created temporary directory "%s"...' % tmp_dir
+
+
+def FtpRetrieve(ftp, filename):
+  ftp.retrbinary('RETR %s' % filename, open(filename, 'wb').write)
+
+
+def FtpUpgrade(ftp, data_filename):
+  """Downloads and repackages the given data from the given FTP server."""
+  SwitchToNewTemporaryDirectory()
+
+  print 'Downloading data...'
+  FtpRetrieve(ftp, data_filename)
+
+  print 'Downloading signature...'
+  signature_filename = '%s.asc' % data_filename
+  FtpRetrieve(ftp, signature_filename)
+
+  print 'Verifying signature...'
+  # If this fails for you, you probably need to import Paul Eggert's public key:
+  # gpg --recv-keys ED97E90E62AA7E34
+  subprocess.check_call(['gpg', '--trusted-key=ED97E90E62AA7E34', '--verify',
+                         signature_filename, data_filename])
+
+  ExtractAndCompile(data_filename)
+
+
+def HttpUpgrade(http, data_filename):
+  """Downloads and repackages the given data from the given HTTP server."""
+  SwitchToNewTemporaryDirectory()
+
+  print 'Downloading data...'
+  http.request("GET", "/time-zones/repository/releases/%s" % data_filename)
+  f = open(data_filename, 'wb')
+  f.write(http.getresponse().read())
+  f.close()
+
+  ExtractAndCompile(data_filename)
+
+
+def ExtractAndCompile(data_filename):
+  new_version = re.search('(tzdata.+)\\.tar\\.gz', data_filename).group(1)
+
+  print 'Extracting...'
+  os.mkdir('extracted')
+  tar = tarfile.open(data_filename, 'r')
+  tar.extractall('extracted')
+
+  print 'Calling zic(1)...'
+  os.mkdir('data')
+  for region in regions:
+    if region != 'backward':
+      subprocess.check_call(['zic', '-d', 'data', 'extracted/%s' % region])
+
+  WriteSetupFile()
+
+  print 'Calling ZoneCompactor to update bionic to %s...' % new_version
+  libcore_src_dir = '%s/../libcore/luni/src/main/java/' % bionic_dir
+  subprocess.check_call(['javac', '-d', '.',
+                         '%s/ZoneCompactor.java' % bionic_libc_tools_zoneinfo_dir,
+                         '%s/libcore/util/ZoneInfo.java' % libcore_src_dir,
+                         '%s/libcore/io/BufferIterator.java' % libcore_src_dir])
+  subprocess.check_call(['java', 'ZoneCompactor',
+                         'setup', 'data', 'extracted/zone.tab',
+                         bionic_libc_zoneinfo_dir, new_version])
+
+
+# Run with no arguments from any directory, with no special setup required.
+# See http://www.iana.org/time-zones/ for more about the source of this data.
+def main():
+  print 'Looking for new tzdata...'
+
+  tzdata_filenames = []
+
+  # The FTP server lets you download intermediate releases, and also lets you
+  # download the signatures for verification, so it's your best choice. It's
+  # also less reliable than the HTTP server, so we support that too as a backup.
+  use_ftp = True
+
+  if use_ftp:
+    ftp = ftplib.FTP('ftp.iana.org')
+    ftp.login()
+    ftp.cwd('tz/releases')
+    for filename in ftp.nlst():
+      if filename.startswith('tzdata20') and filename.endswith('.tar.gz'):
+        tzdata_filenames.append(filename)
+    tzdata_filenames.sort()
+  else:
+    http = httplib.HTTPConnection('www.iana.org')
+    http.request("GET", "/time-zones")
+    index_lines = http.getresponse().read().split('\n')
+    for line in index_lines:
+      m = re.compile('.*href="/time-zones/repository/releases/(tzdata20\d\d\c\.tar\.gz)".*').match(line)
+      if m:
+        tzdata_filenames.append(m.group(1))
+
+  # If you're several releases behind, we'll walk you through the upgrades
+  # one by one.
+  current_version = GetCurrentTzDataVersion()
+  current_filename = '%s.tar.gz' % current_version
+  for filename in tzdata_filenames:
+    if filename > current_filename:
+      print 'Found new tzdata: %s' % filename
+      if use_ftp:
+        FtpUpgrade(ftp, filename)
+      else:
+        HttpUpgrade(http, filename)
+      sys.exit(0)
+
+  print 'You already have the latest tzdata (%s)!' % current_version
+  sys.exit(0)
+
+
+if __name__ == '__main__':
+  main()