diff --git a/README.txt b/README.txt
index 5b7164e..f573a80 100644
--- a/README.txt
+++ b/README.txt
@@ -9,6 +9,7 @@ Prerequisites:
   # Base NilmDB dependencies
   sudo pip3 install cherrypy decorator simplejson requests
   sudo pip3 install python-dateutil tz progressbar psutil
+  sudo pip3 install python-datetime-tz
 
   # Other dependencies (required by some modules)
   sudo pip3 install numpy
diff --git a/nilmdb/utils/datetime_tz/__init__.py b/nilmdb/utils/datetime_tz/__init__.py
deleted file mode 100644
index 0fbd836..0000000
--- a/nilmdb/utils/datetime_tz/__init__.py
+++ /dev/null
@@ -1,710 +0,0 @@
-#!/usr/bin/python
-#
-# Copyright 2009 Google Inc.
-#
-# 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.
-#
-#
-# Disable the invalid name warning as we are inheriting from a standard library
-# object.
-# pylint: disable-msg=C6409,W0212
-
-"""A version of the datetime module which *cares* about timezones.
-
-This module will never return a naive datetime object. This requires the module
-know your local timezone, which it tries really hard to figure out.
-
-You can override the detection by using the datetime.tzaware.defaulttz_set
-method. It the module is unable to figure out the timezone itself this method
-*must* be called before the normal module is imported. If done before importing
-it can also speed up the time taken to import as the defaulttz will no longer
-try and do the detection.
-"""
-
-__author__ = "tansell@google.com (Tim Ansell)"
-
-import calendar
-import datetime
-import os
-import os.path
-import re
-import time
-import warnings
-import dateutil.parser
-import dateutil.relativedelta
-import dateutil.tz
-import pytz
-from . import pytz_abbr
-
-
-try:
-  # pylint: disable-msg=C6204
-  import functools
-except ImportError as e:
-
-  class functools(object):
-    """Fake replacement for a full functools."""
-
-    # pylint: disable-msg=W0613
-    @staticmethod
-    def wraps(f, *args, **kw):
-      return f
-
-
-# Need to patch pytz.utc to have a _utcoffset so you can normalize/localize
-# using it.
-pytz.utc._utcoffset = datetime.timedelta()
-
-
-timedelta = datetime.timedelta
-
-
-def _tzinfome(tzinfo):
-  """Gets a tzinfo object from a string.
-
-  Args:
-    tzinfo: A string (or string like) object, or a datetime.tzinfo object.
-
-  Returns:
-    An datetime.tzinfo object.
-
-  Raises:
-    UnknownTimeZoneError: If the timezone given can't be decoded.
-  """
-  if not isinstance(tzinfo, datetime.tzinfo):
-    try:
-      tzinfo = pytz.timezone(tzinfo)
-    except AttributeError:
-      raise pytz.UnknownTimeZoneError("Unknown timezone! %s" % tzinfo)
-  return tzinfo
-
-
-# Our "local" timezone
-_localtz = None
-
-
-def localtz():
-  """Get the local timezone.
-
-  Returns:
-    The localtime timezone as a tzinfo object.
-  """
-  # pylint: disable-msg=W0603
-  global _localtz
-  if _localtz is None:
-    _localtz = detect_timezone()
-  return _localtz
-
-
-def localtz_set(timezone):
-  """Set the local timezone."""
-  # pylint: disable-msg=W0603
-  global _localtz
-  _localtz = _tzinfome(timezone)
-
-
-def detect_timezone():
-  """Try and detect the timezone that Python is currently running in.
-
-  We have a bunch of different methods for trying to figure this out (listed in
-  order they are attempted).
-    * Try TZ environment variable.
-    * Try and find /etc/timezone file (with timezone name).
-    * Try and find /etc/localtime file (with timezone data).
-    * Try and match a TZ to the current dst/offset/shortname.
-
-  Returns:
-    The detected local timezone as a tzinfo object
-
-  Raises:
-    pytz.UnknownTimeZoneError: If it was unable to detect a timezone.
-  """
-  # First we try the TZ variable
-  tz = _detect_timezone_environ()
-  if tz is not None:
-    return tz
-
-  # Second we try /etc/timezone and use the value in that
-  tz = _detect_timezone_etc_timezone()
-  if tz is not None:
-    return tz
-
-  # Next we try and see if something matches the tzinfo in /etc/localtime
-  tz = _detect_timezone_etc_localtime()
-  if tz is not None:
-    return tz
-
-  # Next we try and use a similiar method to what PHP does.
-  # We first try to search on time.tzname, time.timezone, time.daylight to
-  # match a pytz zone.
-  warnings.warn("Had to fall back to worst detection method (the 'PHP' "
-                "method).")
-
-  tz = _detect_timezone_php()
-  if tz is not None:
-    return tz
-
-  raise pytz.UnknownTimeZoneError("Unable to detect your timezone!")
-
-
-def _detect_timezone_environ():
-  if "TZ" in os.environ:
-    try:
-      return pytz.timezone(os.environ["TZ"])
-    except (IOError, pytz.UnknownTimeZoneError):
-      warnings.warn("You provided a TZ environment value (%r) we did not "
-                    "understand!" % os.environ["TZ"])
-
-
-def _detect_timezone_etc_timezone():
-  if os.path.exists("/etc/timezone"):
-    try:
-      tz = file("/etc/timezone").read().strip()
-      try:
-        return pytz.timezone(tz)
-      except (IOError, pytz.UnknownTimeZoneError) as ei:
-        warnings.warn("Your /etc/timezone file references a timezone (%r) that"
-                      " is not valid (%r)." % (tz, ei))
-
-    # Problem reading the /etc/timezone file
-    except IOError as eo:
-      warnings.warn("Could not access your /etc/timezone file: %s" % eo)
-
-
-def _detect_timezone_etc_localtime():
-  matches = []
-  if os.path.exists("/etc/localtime"):
-    localtime = pytz.tzfile.build_tzinfo("/etc/localtime",
-                                         file("/etc/localtime"))
-
-    # See if we can find a "Human Name" for this..
-    for tzname in pytz.all_timezones:
-      tz = _tzinfome(tzname)
-
-      if dir(tz) != dir(localtime):
-        continue
-
-      for attrib in dir(tz):
-        # Ignore functions and specials
-        if callable(getattr(tz, attrib)) or attrib.startswith("__"):
-          continue
-
-        # This will always be different
-        if attrib == "zone" or attrib == "_tzinfos":
-          continue
-
-        if getattr(tz, attrib) != getattr(localtime, attrib):
-          break
-
-      # We get here iff break didn't happen, i.e. no meaningful attributes
-      # differ between tz and localtime
-      else:
-        matches.append(tzname)
-
-    if len(matches) == 1:
-      return _tzinfome(matches[0])
-    else:
-      # Warn the person about this!
-      warning = "Could not get a human name for your timezone: "
-      if len(matches) > 1:
-        warning += ("We detected multiple matches for your /etc/localtime. "
-                    "(Matches where %s)" % matches)
-        return _tzinfome(matches[0])
-      else:
-        warning += "We detected no matches for your /etc/localtime."
-      warnings.warn(warning)
-
-      # Register /etc/localtime as the timezone loaded.
-      pytz._tzinfo_cache['/etc/localtime'] = localtime
-      return localtime
-
-
-def _detect_timezone_php():
-  tomatch = (time.tzname[0], time.timezone, time.daylight)
-  now = datetime.datetime.now()
-
-  matches = []
-  for tzname in pytz.all_timezones:
-    try:
-      tz = pytz.timezone(tzname)
-    except IOError:
-      continue
-
-    try:
-      indst = tz.localize(now).timetuple()[-1]
-
-      if tomatch == (tz._tzname, -tz._utcoffset.seconds, indst):
-        matches.append(tzname)
-
-    # pylint: disable-msg=W0704
-    except AttributeError:
-      pass
-
-  if len(matches) > 1:
-    warnings.warn("We detected multiple matches for the timezone, choosing "
-                  "the first %s. (Matches where %s)" % (matches[0], matches))
-    return pytz.timezone(matches[0])
-
-
-class datetime_tz(datetime.datetime):
-  """An extension of the inbuilt datetime adding more functionality.
-
-  The extra functionality includes:
-    * Partial parsing support (IE 2006/02/30 matches %Y/%M/%D %H:%M)
-    * Full integration with pytz (just give it the string of the timezone!)
-    * Proper support for going to/from Unix timestamps (which are in UTC!).
-  """
-  __slots__ = ["is_dst"]
-
-  def __new__(cls, *args, **kw):
-    args = list(args)
-    if not args:
-      raise TypeError("Not enough arguments given.")
-
-    # See if we are given a tzinfo object...
-    tzinfo = None
-    if isinstance(args[-1], (datetime.tzinfo, str)):
-      tzinfo = _tzinfome(args.pop(-1))
-    elif kw.get("tzinfo", None) is not None:
-      tzinfo = _tzinfome(kw.pop("tzinfo"))
-
-    # Create a datetime object if we don't have one
-    if isinstance(args[0], datetime.datetime):
-      # Convert the datetime instance to a datetime object.
-      newargs = (list(args[0].timetuple()[0:6]) +
-                 [args[0].microsecond, args[0].tzinfo])
-      dt = datetime.datetime(*newargs)
-
-      if tzinfo is None and dt.tzinfo is None:
-        raise TypeError("Must specify a timezone!")
-
-      if tzinfo is not None and dt.tzinfo is not None:
-        raise TypeError("Can not give a timezone with timezone aware"
-                        " datetime object! (Use localize.)")
-    else:
-      dt = datetime.datetime(*args, **kw)
-
-    if dt.tzinfo is not None:
-      # Re-normalize the dt object
-      dt = dt.tzinfo.normalize(dt)
-
-    else:
-      if tzinfo is None:
-        tzinfo = localtz()
-
-      try:
-        dt = tzinfo.localize(dt, is_dst=None)
-      except pytz.AmbiguousTimeError:
-        is_dst = None
-        if "is_dst" in kw:
-          is_dst = kw.pop("is_dst")
-
-        try:
-          dt = tzinfo.localize(dt, is_dst)
-        except IndexError:
-          raise pytz.AmbiguousTimeError("No such time exists!")
-
-    newargs = list(dt.timetuple()[0:6])+[dt.microsecond, dt.tzinfo]
-    obj = datetime.datetime.__new__(cls, *newargs)
-    obj.is_dst = obj.dst() != datetime.timedelta(0)
-    return obj
-
-  def asdatetime(self, naive=True):
-    """Return this datetime_tz as a datetime object.
-
-    Args:
-      naive: Return *without* any tz info.
-
-    Returns:
-      This datetime_tz as a datetime object.
-    """
-    args = list(self.timetuple()[0:6])+[self.microsecond]
-    if not naive:
-      args.append(self.tzinfo)
-    return datetime.datetime(*args)
-
-  def asdate(self):
-    """Return this datetime_tz as a date object.
-
-    Returns:
-      This datetime_tz as a date object.
-    """
-    return datetime.date(self.year, self.month, self.day)
-
-  def totimestamp(self):
-    """Convert this datetime object back to a unix timestamp.
-
-    The Unix epoch is the time 00:00:00 UTC on January 1, 1970.
-
-    Returns:
-      Unix timestamp.
-    """
-    return calendar.timegm(self.utctimetuple())+1e-6*self.microsecond
-
-  def astimezone(self, tzinfo):
-    """Returns a version of this timestamp converted to the given timezone.
-
-    Args:
-      tzinfo: Either a datetime.tzinfo object or a string (which will be looked
-              up in pytz.
-
-    Returns:
-      A datetime_tz object in the given timezone.
-    """
-    # Assert we are not a naive datetime object
-    assert self.tzinfo is not None
-
-    tzinfo = _tzinfome(tzinfo)
-
-    d = self.asdatetime(naive=False).astimezone(tzinfo)
-    return datetime_tz(d)
-
-  # pylint: disable-msg=C6113
-  def replace(self, **kw):
-    """Return datetime with new specified fields given as arguments.
-
-    For example, dt.replace(days=4) would return a new datetime_tz object with
-    exactly the same as dt but with the days attribute equal to 4.
-
-    Any attribute can be replaced, but tzinfo can not be set to None.
-
-    Args:
-      Any datetime_tz attribute.
-
-    Returns:
-      A datetime_tz object with the attributes replaced.
-
-    Raises:
-      TypeError: If the given replacement is invalid.
-    """
-    if "tzinfo" in kw:
-      if kw["tzinfo"] is None:
-        raise TypeError("Can not remove the timezone use asdatetime()")
-
-    is_dst = None
-    if "is_dst" in kw:
-      is_dst = kw["is_dst"]
-      del kw["is_dst"]
-    else:
-      # Use our own DST setting..
-      is_dst = self.is_dst
-
-    replaced = self.asdatetime().replace(**kw)
-
-    return datetime_tz(replaced, tzinfo=self.tzinfo.zone, is_dst=is_dst)
-
-  # pylint: disable-msg=C6310
-  @classmethod
-  def smartparse(cls, toparse, tzinfo=None):
-    """Method which uses dateutil.parse and extras to try and parse the string.
-
-    Valid dates are found at:
-     http://labix.org/python-dateutil#head-1443e0f14ad5dff07efd465e080d1110920673d8-2
-
-    Other valid formats include:
-      "now" or "today"
-      "yesterday"
-      "tommorrow"
-      "5 minutes ago"
-      "10 hours ago"
-      "10h5m ago"
-      "start of yesterday"
-      "end of tommorrow"
-      "end of 3rd of March"
-
-    Args:
-      toparse: The string to parse.
-      tzinfo: Timezone for the resultant datetime_tz object should be in.
-              (Defaults to your local timezone.)
-
-    Returns:
-      New datetime_tz object.
-
-    Raises:
-      ValueError: If unable to make sense of the input.
-    """
-    # Default for empty fields are:
-    #  year/month/day == now
-    #  hour/minute/second/microsecond == 0
-    toparse = toparse.strip()
-
-    if tzinfo is None:
-      dt = cls.now()
-    else:
-      dt = cls.now(tzinfo)
-
-    default = dt.replace(hour=0, minute=0, second=0, microsecond=0)
-
-    # Remove "start of " and "end of " prefix in the string
-    if toparse.lower().startswith("end of "):
-      toparse = toparse[7:].strip()
-
-      dt += datetime.timedelta(days=1)
-      dt = dt.replace(hour=0, minute=0, second=0, microsecond=0)
-      dt -= datetime.timedelta(microseconds=1)
-
-      default = dt
-
-    elif toparse.lower().startswith("start of "):
-      toparse = toparse[9:].strip()
-
-      dt = dt.replace(hour=0, minute=0, second=0, microsecond=0)
-      default = dt
-
-    # Handle strings with "now", "today", "yesterday", "tomorrow" and "ago".
-    # Need to use lowercase
-    toparselower = toparse.lower()
-
-    if toparselower in ["now", "today"]:
-      pass
-
-    elif toparselower == "yesterday":
-      dt -= datetime.timedelta(days=1)
-
-    elif toparselower == "tommorrow":
-      dt += datetime.timedelta(days=1)
-
-    elif "ago" in toparselower:
-      # Remove the "ago" bit
-      toparselower = toparselower[:-3]
-      # Replace all "a day and an hour" with "1 day 1 hour"
-      toparselower = toparselower.replace("a ", "1 ")
-      toparselower = toparselower.replace("an ", "1 ")
-      toparselower = toparselower.replace(" and ", " ")
-
-      # Match the following
-      # 1 hour ago
-      # 1h ago
-      # 1 h ago
-      # 1 hour ago
-      # 2 hours ago
-      # Same with minutes, seconds, etc.
-
-      tocheck = ("seconds", "minutes", "hours", "days", "weeks", "months",
-                 "years")
-      result = {}
-      for match in re.finditer("([0-9]+)([^0-9]*)", toparselower):
-        amount = int(match.group(1))
-        unit = match.group(2).strip()
-
-        for bit in tocheck:
-          regex = "^([%s]|((%s)s?))$" % (
-              bit[0], bit[:-1])
-
-          bitmatch = re.search(regex, unit)
-          if bitmatch:
-            result[bit] = amount
-            break
-        else:
-          raise ValueError("Was not able to parse date unit %r!" % unit)
-
-      delta = dateutil.relativedelta.relativedelta(**result)
-      dt -= delta
-
-    else:
-      # Handle strings with normal datetime format, use original case.
-      dt = dateutil.parser.parse(toparse, default=default.asdatetime(),
-                                 tzinfos=pytz_abbr.tzinfos)
-      if dt is None:
-        raise ValueError("Was not able to parse date!")
-
-      if dt.tzinfo is pytz_abbr.unknown:
-        dt = dt.replace(tzinfo=None)
-
-      if dt.tzinfo is None:
-        if tzinfo is None:
-          tzinfo = localtz()
-        dt = cls(dt, tzinfo)
-      else:
-        if isinstance(dt.tzinfo, pytz_abbr.tzabbr):
-          abbr = dt.tzinfo
-          dt = dt.replace(tzinfo=None)
-          dt = cls(dt, abbr.zone, is_dst=abbr.dst)
-
-        dt = cls(dt)
-
-    return dt
-
-  @classmethod
-  def utcfromtimestamp(cls, timestamp):
-    """Returns a datetime object of a given timestamp (in UTC)."""
-    obj = datetime.datetime.utcfromtimestamp(timestamp)
-    obj = pytz.utc.localize(obj)
-    return cls(obj)
-
-  @classmethod
-  def fromtimestamp(cls, timestamp):
-    """Returns a datetime object of a given timestamp (in local tz)."""
-    d = cls.utcfromtimestamp(timestamp)
-    return d.astimezone(localtz())
-
-  @classmethod
-  def utcnow(cls):
-    """Return a new datetime representing UTC day and time."""
-    obj = datetime.datetime.utcnow()
-    obj = cls(obj, tzinfo=pytz.utc)
-    return obj
-
-  @classmethod
-  def now(cls, tzinfo=None):
-    """[tz] -> new datetime with tz's local day and time."""
-    obj = cls.utcnow()
-    if tzinfo is None:
-      tzinfo = localtz()
-    return obj.astimezone(tzinfo)
-
-  today = now
-
-  @staticmethod
-  def fromordinal(ordinal):
-    raise SyntaxError("Not enough information to create a datetime_tz object "
-                      "from an ordinal. Please use datetime.date.fromordinal")
-
-
-class iterate(object):
-  """Helpful iterators for working with datetime_tz objects."""
-
-  @staticmethod
-  def between(start, delta, end=None):
-    """Return an iterator between this date till given end point.
-
-    Example usage:
-      >>> d = datetime_tz.smartparse("5 days ago")
-      2008/05/12 11:45
-      >>> for i in d.between(timedelta(days=1), datetime_tz.now()):
-      >>>    print i
-      2008/05/12 11:45
-      2008/05/13 11:45
-      2008/05/14 11:45
-      2008/05/15 11:45
-      2008/05/16 11:45
-
-    Args:
-      start: The date to start at.
-      delta: The interval to iterate with.
-      end: (Optional) Date to end at. If not given the iterator will never
-           terminate.
-
-    Yields:
-      datetime_tz objects.
-    """
-    toyield = start
-    while end is None or toyield < end:
-      yield toyield
-      toyield += delta
-
-  @staticmethod
-  def weeks(start, end=None):
-    """Iterate over the weeks between the given datetime_tzs.
-
-    Args:
-      start: datetime_tz to start from.
-      end: (Optional) Date to end at, if not given the iterator will never
-           terminate.
-
-    Returns:
-      An iterator which generates datetime_tz objects a week apart.
-    """
-    return iterate.between(start, datetime.timedelta(days=7), end)
-
-  @staticmethod
-  def days(start, end=None):
-    """Iterate over the days between the given datetime_tzs.
-
-    Args:
-      start: datetime_tz to start from.
-      end: (Optional) Date to end at, if not given the iterator will never
-           terminate.
-
-    Returns:
-      An iterator which generates datetime_tz objects a day apart.
-    """
-    return iterate.between(start, datetime.timedelta(days=1), end)
-
-  @staticmethod
-  def hours(start, end=None):
-    """Iterate over the hours between the given datetime_tzs.
-
-    Args:
-      start: datetime_tz to start from.
-      end: (Optional) Date to end at, if not given the iterator will never
-           terminate.
-
-    Returns:
-      An iterator which generates datetime_tz objects a hour apart.
-    """
-    return iterate.between(start, datetime.timedelta(hours=1), end)
-
-  @staticmethod
-  def minutes(start, end=None):
-    """Iterate over the minutes between the given datetime_tzs.
-
-    Args:
-      start: datetime_tz to start from.
-      end: (Optional) Date to end at, if not given the iterator will never
-           terminate.
-
-    Returns:
-      An iterator which generates datetime_tz objects a minute apart.
-    """
-    return iterate.between(start, datetime.timedelta(minutes=1), end)
-
-  @staticmethod
-  def seconds(start, end=None):
-    """Iterate over the seconds between the given datetime_tzs.
-
-    Args:
-      start: datetime_tz to start from.
-      end: (Optional) Date to end at, if not given the iterator will never
-           terminate.
-
-    Returns:
-      An iterator which generates datetime_tz objects a second apart.
-    """
-    return iterate.between(start, datetime.timedelta(minutes=1), end)
-
-
-def _wrap_method(name):
-  """Wrap a method.
-
-  Patch a method which might return a datetime.datetime to return a
-  datetime_tz.datetime_tz instead.
-
-  Args:
-    name: The name of the method to patch
-  """
-  method = getattr(datetime.datetime, name)
-
-  # Have to give the second argument as method has no __module__ option.
-  @functools.wraps(method, ("__name__", "__doc__"), ())
-  def wrapper(*args, **kw):
-    r = method(*args, **kw)
-
-    if isinstance(r, datetime.datetime) and not isinstance(r, datetime_tz):
-      r = datetime_tz(r)
-    return r
-
-  setattr(datetime_tz, name, wrapper)
-
-for methodname in ["__add__", "__radd__", "__rsub__", "__sub__", "combine"]:
-
-  # Make sure we have not already got an override for this method
-  assert methodname not in datetime_tz.__dict__
-
-  _wrap_method(methodname)
-
-
-__all__ = ['datetime_tz', 'detect_timezone', 'iterate', 'localtz',
-    'localtz_set', 'timedelta', '_detect_timezone_environ',
-    '_detect_timezone_etc_localtime', '_detect_timezone_etc_timezone',
-    '_detect_timezone_php']
diff --git a/nilmdb/utils/datetime_tz/pytz_abbr.py b/nilmdb/utils/datetime_tz/pytz_abbr.py
deleted file mode 100644
index 689ef2e..0000000
--- a/nilmdb/utils/datetime_tz/pytz_abbr.py
+++ /dev/null
@@ -1,230 +0,0 @@
-#!/usr/bin/python2.4
-# -*- coding: utf-8 -*-
-#
-# Copyright 2010 Google Inc. All Rights Reserved.
-#
-
-"""
-Common time zone acronyms/abbreviations for use with the datetime_tz module.
-
-*WARNING*: There are lots of caveats when using this module which are listed
-below.
-
-CAVEAT 1: The acronyms/abbreviations are not globally unique, they are not even
-unique within a region. For example, EST can mean any of,
-  Eastern Standard Time in Australia (which is 10 hour ahead of UTC)
-  Eastern Standard Time in North America (which is 5 hours behind UTC)
-
-Where there are two abbreviations the more popular one will appear in the all
-dictionary, while the less common one will only appear in that countries region
-dictionary. IE If using all, EST will be mapped to Eastern Standard Time in
-North America.
-
-CAVEAT 2: Many of the acronyms don't map to a neat Oslon timezones. For example,
-Eastern European Summer Time (EEDT) is used by many different countries in
-Europe *at different times*! If the acronym does not map neatly to one zone it
-is mapped to the Etc/GMT+-XX Oslon zone. This means that any date manipulations
-can end up with idiot things like summer time in the middle of winter.
-
-CAVEAT 3: The Summer/Standard time difference is really important! For an hour
-each year it is needed to determine which time you are actually talking about.
-    2002-10-27 01:20:00 EST != 2002-10-27 01:20:00 EDT
-"""
-
-import datetime
-import pytz
-import pytz.tzfile
-
-
-class tzabbr(datetime.tzinfo):
-  """A timezone abbreviation.
-
-  *WARNING*: This is not a tzinfo implementation! Trying to use this as tzinfo
-  object will result in failure.  We inherit from datetime.tzinfo so we can get
-  through the dateutil checks.
-  """
-  pass
-
-
-# A "marker" tzinfo object which is used to signify an unknown timezone.
-unknown = datetime.tzinfo(0)
-
-
-regions = {'all': {}, 'military': {}}
-# Create a special alias for the all and military regions
-all = regions['all']
-military = regions['military']
-
-
-def tzabbr_register(abbr, name, region, zone, dst):
-  """Register a new timezone abbreviation in the global registry.
-
-  If another abbreviation with the same name has already been registered it new
-  abbreviation will only be registered in region specific dictionary.
-  """
-  newabbr = tzabbr()
-  newabbr.abbr = abbr
-  newabbr.name = name
-  newabbr.region = region
-  newabbr.zone = zone
-  newabbr.dst = dst
-
-  if abbr not in all:
-    all[abbr] = newabbr
-
-  if not region in regions:
-    regions[region] = {}
-
-  assert abbr not in regions[region]
-  regions[region][abbr] = newabbr
-
-
-def tzinfos_create(use_region):
-  abbrs = regions[use_region]
-
-  def tzinfos(abbr, offset):
-    if abbr:
-      if abbr in abbrs:
-        result = abbrs[abbr]
-        if offset:
-          # FIXME: Check the offset matches the abbreviation we just selected.
-          pass
-        return result
-      else:
-        raise ValueError("Unknown timezone found %s" % abbr)
-    if offset == 0:
-      return pytz.utc
-    if offset:
-      return pytz.FixedOffset(offset/60)
-    return unknown
-
-  return tzinfos
-
-
-# Create a special alias for the all tzinfos
-tzinfos = tzinfos_create('all')
-
-
-# Create the abbreviations.
-# *WARNING*: Order matters!
-tzabbr_register("A", "Alpha Time Zone", "Military", "Etc/GMT-1", False)
-tzabbr_register("ACDT", "Australian Central Daylight Time", "Australia",
-                "Australia/Adelaide", True)
-tzabbr_register("ACST", "Australian Central Standard Time", "Australia",
-                "Australia/Adelaide", False)
-tzabbr_register("ADT", "Atlantic Daylight Time", "North America",
-                "America/Halifax", True)
-tzabbr_register("AEDT", "Australian Eastern Daylight Time", "Australia",
-                "Australia/Sydney", True)
-tzabbr_register("AEST", "Australian Eastern Standard Time", "Australia",
-                "Australia/Sydney", False)
-tzabbr_register("AKDT", "Alaska Daylight Time", "North America",
-                "US/Alaska", True)
-tzabbr_register("AKST", "Alaska Standard Time", "North America",
-                "US/Alaska", False)
-tzabbr_register("AST", "Atlantic Standard Time", "North America",
-                "America/Halifax", False)
-tzabbr_register("AWDT", "Australian Western Daylight Time", "Australia",
-                "Australia/West", True)
-tzabbr_register("AWST", "Australian Western Standard Time", "Australia",
-                "Australia/West", False)
-tzabbr_register("B", "Bravo Time Zone", "Military", "Etc/GMT-2", False)
-tzabbr_register("BST", "British Summer Time", "Europe", "Europe/London", True)
-tzabbr_register("C", "Charlie Time Zone", "Military", "Etc/GMT-2", False)
-tzabbr_register("CDT", "Central Daylight Time", "North America",
-                "US/Central", True)
-tzabbr_register("CEDT", "Central European Daylight Time", "Europe",
-                "Etc/GMT+2", True)
-tzabbr_register("CEST", "Central European Summer Time", "Europe",
-                "Etc/GMT+2", True)
-tzabbr_register("CET", "Central European Time", "Europe", "Etc/GMT+1", False)
-tzabbr_register("CST", "Central Standard Time", "North America",
-                "US/Central", False)
-tzabbr_register("CXT", "Christmas Island Time", "Australia",
-                "Indian/Christmas", False)
-tzabbr_register("D", "Delta Time Zone", "Military", "Etc/GMT-2", False)
-tzabbr_register("E", "Echo Time Zone", "Military", "Etc/GMT-2", False)
-tzabbr_register("EDT", "Eastern Daylight Time", "North America",
-                "US/Eastern", True)
-tzabbr_register("EEDT", "Eastern European Daylight Time", "Europe",
-                "Etc/GMT+3", True)
-tzabbr_register("EEST", "Eastern European Summer Time", "Europe",
-                "Etc/GMT+3", True)
-tzabbr_register("EET", "Eastern European Time", "Europe", "Etc/GMT+2", False)
-tzabbr_register("EST", "Eastern Standard Time", "North America",
-                "US/Eastern", False)
-tzabbr_register("F", "Foxtrot Time Zone", "Military", "Etc/GMT-6", False)
-tzabbr_register("G", "Golf Time Zone", "Military", "Etc/GMT-7", False)
-tzabbr_register("GMT", "Greenwich Mean Time", "Europe", pytz.utc, False)
-tzabbr_register("H", "Hotel Time Zone", "Military", "Etc/GMT-8", False)
-#tzabbr_register("HAA", u"Heure Avancée de l'Atlantique", u"North America", u"UTC - 3 hours")
-#tzabbr_register("HAC", u"Heure Avancée du Centre", u"North America", u"UTC - 5 hours")
-tzabbr_register("HADT", "Hawaii-Aleutian Daylight Time", "North America",
-                "Pacific/Honolulu", True)
-#tzabbr_register("HAE", u"Heure Avancée de l'Est", u"North America", u"UTC - 4 hours")
-#tzabbr_register("HAP", u"Heure Avancée du Pacifique", u"North America", u"UTC - 7 hours")
-#tzabbr_register("HAR", u"Heure Avancée des Rocheuses", u"North America", u"UTC - 6 hours")
-tzabbr_register("HAST", "Hawaii-Aleutian Standard Time", "North America",
-                "Pacific/Honolulu", False)
-#tzabbr_register("HAT", u"Heure Avancée de Terre-Neuve", u"North America", u"UTC - 2:30 hours")
-#tzabbr_register("HAY", u"Heure Avancée du Yukon", u"North America", u"UTC - 8 hours")
-tzabbr_register("HDT", "Hawaii Daylight Time", "North America",
-                "Pacific/Honolulu", True)
-#tzabbr_register("HNA", u"Heure Normale de l'Atlantique", u"North America", u"UTC - 4 hours")
-#tzabbr_register("HNC", u"Heure Normale du Centre", u"North America", u"UTC - 6 hours")
-#tzabbr_register("HNE", u"Heure Normale de l'Est", u"North America", u"UTC - 5 hours")
-#tzabbr_register("HNP", u"Heure Normale du Pacifique", u"North America", u"UTC - 8 hours")
-#tzabbr_register("HNR", u"Heure Normale des Rocheuses", u"North America", u"UTC - 7 hours")
-#tzabbr_register("HNT", u"Heure Normale de Terre-Neuve", u"North America", u"UTC - 3:30 hours")
-#tzabbr_register("HNY", u"Heure Normale du Yukon", u"North America", u"UTC - 9 hours")
-tzabbr_register("HST", "Hawaii Standard Time", "North America",
-                "Pacific/Honolulu", False)
-tzabbr_register("I", "India Time Zone", "Military", "Etc/GMT-9", False)
-tzabbr_register("IST", "Irish Summer Time", "Europe", "Europe/Dublin", True)
-tzabbr_register("K", "Kilo Time Zone", "Military", "Etc/GMT-10", False)
-tzabbr_register("L", "Lima Time Zone", "Military", "Etc/GMT-11", False)
-tzabbr_register("M", "Mike Time Zone", "Military", "Etc/GMT-12", False)
-tzabbr_register("MDT", "Mountain Daylight Time", "North America",
-                "US/Mountain", True)
-#tzabbr_register("MESZ", u"Mitteleuroäische Sommerzeit", u"Europe", u"UTC + 2 hours")
-#tzabbr_register("MEZ", u"Mitteleuropäische Zeit", u"Europe", u"UTC + 1 hour")
-tzabbr_register("MSD", "Moscow Daylight Time", "Europe",
-                "Europe/Moscow", True)
-tzabbr_register("MSK", "Moscow Standard Time", "Europe",
-                "Europe/Moscow", False)
-tzabbr_register("MST", "Mountain Standard Time", "North America",
-                "US/Mountain", False)
-tzabbr_register("N", "November Time Zone", "Military", "Etc/GMT+1", False)
-tzabbr_register("NDT", "Newfoundland Daylight Time", "North America",
-                "America/St_Johns", True)
-tzabbr_register("NFT", "Norfolk (Island) Time", "Australia",
-                "Pacific/Norfolk", False)
-tzabbr_register("NST", "Newfoundland Standard Time", "North America",
-                "America/St_Johns", False)
-tzabbr_register("O", "Oscar Time Zone", "Military", "Etc/GMT+2", False)
-tzabbr_register("P", "Papa Time Zone", "Military", "Etc/GMT+3", False)
-tzabbr_register("PDT", "Pacific Daylight Time", "North America",
-                "US/Pacific", True)
-tzabbr_register("PST", "Pacific Standard Time", "North America",
-                "US/Pacific", False)
-tzabbr_register("Q", "Quebec Time Zone", "Military", "Etc/GMT+4", False)
-tzabbr_register("R", "Romeo Time Zone", "Military", "Etc/GMT+5", False)
-tzabbr_register("S", "Sierra Time Zone", "Military", "Etc/GMT+6", False)
-tzabbr_register("T", "Tango Time Zone", "Military", "Etc/GMT+7", False)
-tzabbr_register("U", "Uniform Time Zone", "Military", "Etc/GMT+8", False)
-tzabbr_register("UTC", "Coordinated Universal Time", "Europe",
-                pytz.utc, False)
-tzabbr_register("V", "Victor Time Zone", "Military", "Etc/GMT+9", False)
-tzabbr_register("W", "Whiskey Time Zone", "Military", "Etc/GMT+10", False)
-tzabbr_register("WDT", "Western Daylight Time", "Australia",
-                "Australia/West", True)
-tzabbr_register("WEDT", "Western European Daylight Time", "Europe",
-                "Etc/GMT+1", True)
-tzabbr_register("WEST", "Western European Summer Time", "Europe",
-                "Etc/GMT+1", True)
-tzabbr_register("WET", "Western European Time", "Europe", pytz.utc, False)
-tzabbr_register("WST", "Western Standard Time", "Australia",
-                "Australia/West", False)
-tzabbr_register("X", "X-ray Time Zone", "Military", "Etc/GMT+11", False)
-tzabbr_register("Y", "Yankee Time Zone", "Military", "Etc/GMT+12", False)
-tzabbr_register("Z", "Zulu Time Zone", "Military", pytz.utc, False)
diff --git a/nilmdb/utils/time.py b/nilmdb/utils/time.py
index d31bb5d..bbae7ee 100644
--- a/nilmdb/utils/time.py
+++ b/nilmdb/utils/time.py
@@ -1,6 +1,4 @@
-
-
-from nilmdb.utils import datetime_tz
+import datetime_tz
 import re
 import time
 
diff --git a/nilmdb/utils/timestamper.py b/nilmdb/utils/timestamper.py
index e476d3c..1363491 100644
--- a/nilmdb/utils/timestamper.py
+++ b/nilmdb/utils/timestamper.py
@@ -69,7 +69,7 @@ class TimestamperRate(Timestamper):
             while True:
                 now = start + rate_to_period(rate, n)
                 if end and now >= end:
-                    raise StopIteration
+                    return
                 yield timestamp_to_string(now) + " "
                 n += 1
         Timestamper.__init__(self, infile, iterator(start, rate, end))
diff --git a/tests/test_interval.py b/tests/test_interval.py
index e20730c..b325592 100644
--- a/tests/test_interval.py
+++ b/tests/test_interval.py
@@ -2,7 +2,7 @@
 
 import nilmdb
 from nilmdb.utils.printf import *
-from nilmdb.utils import datetime_tz
+import datetime_tz
 
 from nose.tools import *
 from nose.tools import assert_raises
diff --git a/tests/test_timestamper.py b/tests/test_timestamper.py
index e537ff7..d7c646b 100644
--- a/tests/test_timestamper.py
+++ b/tests/test_timestamper.py
@@ -1,6 +1,6 @@
 import nilmdb
 from nilmdb.utils.printf import *
-from nilmdb.utils import datetime_tz
+import datetime_tz
 
 from nose.tools import *
 from nose.tools import assert_raises