diff --git a/.circleci/config.yml b/.circleci/config.yml
index 15dda14a80b..101357a36da 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -310,7 +310,7 @@ jobs:
       - checkout
       - run:
           name: Install tox
-          command: 'sudo pip install tox requests black pytz decorator retrying inflect'
+          command: 'sudo pip install retrying tox black inflect'
       - run:
           name: Update jupyterlab-plotly version
           command: 'cd packages/python/plotly; python setup.py updateplotlywidgetversion'
diff --git a/.circleci/create_conda_optional_env.sh b/.circleci/create_conda_optional_env.sh
index 8caae9bae72..3cbbc63966a 100755
--- a/.circleci/create_conda_optional_env.sh
+++ b/.circleci/create_conda_optional_env.sh
@@ -16,7 +16,7 @@ if [ ! -d $HOME/miniconda/envs/circle_optional ]; then
     # Create environment
     # PYTHON_VERSION=3.6
     $HOME/miniconda/bin/conda create -n circle_optional --yes python=$PYTHON_VERSION \
-requests six pytz retrying psutil pandas decorator pytest mock nose poppler xarray scikit-image ipython
+requests nbformat six retrying psutil pandas decorator pytest mock nose poppler xarray scikit-image ipython
 
     # Install orca into environment
     $HOME/miniconda/bin/conda install --yes -n circle_optional -c plotly plotly-orca
diff --git a/packages/python/plotly/_plotly_utils/utils.py b/packages/python/plotly/_plotly_utils/utils.py
index 07e6447cdde..26face3c25f 100644
--- a/packages/python/plotly/_plotly_utils/utils.py
+++ b/packages/python/plotly/_plotly_utils/utils.py
@@ -1,9 +1,7 @@
-import datetime
 import decimal
 import json as _json
 import sys
 import re
-import pytz
 
 from _plotly_utils.optional_imports import get_module
 
@@ -102,7 +100,7 @@ def default(self, obj):
             self.encode_as_sage,
             self.encode_as_numpy,
             self.encode_as_pandas,
-            self.encode_as_datetime_v4,
+            self.encode_as_datetime,
             self.encode_as_date,
             self.encode_as_list,  # because some values have `tolist` do last.
             self.encode_as_decimal,
@@ -169,42 +167,13 @@ def encode_as_numpy(obj):
             raise NotEncodable
 
     @staticmethod
-    def encode_as_datetime_v4(obj):
+    def encode_as_datetime(obj):
         """Convert datetime objects to iso-format strings"""
         try:
             return obj.isoformat()
         except AttributeError:
             raise NotEncodable
 
-    @staticmethod
-    def encode_as_datetime(obj):
-        """Attempt to convert to utc-iso time string using datetime methods."""
-        # Since PY36, isoformat() converts UTC
-        # datetime.datetime objs to UTC T04:00:00
-        if not (
-            PY36_OR_LATER
-            and (isinstance(obj, datetime.datetime) and obj.tzinfo is None)
-        ):
-            try:
-                obj = obj.astimezone(pytz.utc)
-            except ValueError:
-                # we'll get a value error if trying to convert with naive datetime
-                pass
-            except TypeError:
-                # pandas throws a typeerror here instead of a value error, it's OK
-                pass
-            except AttributeError:
-                # we'll get an attribute error if astimezone DNE
-                raise NotEncodable
-
-        # now we need to get a nicely formatted time string
-        try:
-            time_string = obj.isoformat()
-        except AttributeError:
-            raise NotEncodable
-        else:
-            return iso_to_plotly_time_string(time_string)
-
     @staticmethod
     def encode_as_date(obj):
         """Attempt to convert to utc-iso time string using date methods."""
diff --git a/packages/python/plotly/optional-requirements.txt b/packages/python/plotly/optional-requirements.txt
index d173261994d..d0bb959e0d9 100644
--- a/packages/python/plotly/optional-requirements.txt
+++ b/packages/python/plotly/optional-requirements.txt
@@ -18,6 +18,10 @@ nose==1.3.3
 pytest==3.5.1
 backports.tempfile==1.0
 xarray
+pytz
+
+## orca dependencies ##
+requests
 psutil
 
 ## code formatting
diff --git a/packages/python/plotly/plotly/io/_orca.py b/packages/python/plotly/plotly/io/_orca.py
index 5795daf3e80..2f3608bfb3d 100644
--- a/packages/python/plotly/plotly/io/_orca.py
+++ b/packages/python/plotly/plotly/io/_orca.py
@@ -1325,6 +1325,20 @@ def ensure_server():
 """
         )
 
+    # Validate requests
+    if not get_module("requests"):
+        raise ValueError(
+            """\
+Image generation requires the requests package.
+
+Install using pip:
+    $ pip install requests
+
+Install using conda:
+    $ conda install requests
+"""
+        )
+
     # Validate orca executable
     if status.state == "unvalidated":
         validate_executable()
diff --git a/packages/python/plotly/plotly/io/_renderers.py b/packages/python/plotly/plotly/io/_renderers.py
index c39d0c32e8a..ba11850cb51 100644
--- a/packages/python/plotly/plotly/io/_renderers.py
+++ b/packages/python/plotly/plotly/io/_renderers.py
@@ -5,6 +5,7 @@
 
 import six
 import os
+from distutils.version import LooseVersion
 
 from plotly import optional_imports
 
@@ -27,6 +28,7 @@
 
 ipython = optional_imports.get_module("IPython")
 ipython_display = optional_imports.get_module("IPython.display")
+nbformat = optional_imports.get_module("nbformat")
 
 
 # Renderer configuration class
@@ -374,6 +376,11 @@ def show(fig, renderer=None, validate=True, **kwargs):
                 "Mime type rendering requires ipython but it is not installed"
             )
 
+        if not nbformat or LooseVersion(nbformat.__version__) < LooseVersion("4.2.0"):
+            raise ValueError(
+                "Mime type rendering requires nbformat>=4.2.0 but it is not installed"
+            )
+
         ipython_display.display(bundle, raw=True)
 
     # external renderers
diff --git a/packages/python/plotly/plotly/matplotlylib/mpltools.py b/packages/python/plotly/plotly/matplotlylib/mpltools.py
index 2a432bd68be..af2e7d38617 100644
--- a/packages/python/plotly/plotly/matplotlylib/mpltools.py
+++ b/packages/python/plotly/plotly/matplotlylib/mpltools.py
@@ -5,10 +5,10 @@
 
 """
 import math
-import warnings
+import datetime
 
+import warnings
 import matplotlib.dates
-import pytz
 
 
 def check_bar_match(old_bar, new_bar):
@@ -542,7 +542,7 @@ def mpl_dates_to_datestrings(dates, mpl_formatter):
     if mpl_formatter == "TimeSeries_DateFormatter":
         try:
             dates = matplotlib.dates.epoch2num([date * 24 * 60 * 60 for date in dates])
-            dates = matplotlib.dates.num2date(dates, tz=pytz.utc)
+            dates = matplotlib.dates.num2date(dates)
         except:
             return _dates
 
@@ -551,7 +551,7 @@ def mpl_dates_to_datestrings(dates, mpl_formatter):
     # according to mpl --> try num2date(1)
     else:
         try:
-            dates = matplotlib.dates.num2date(dates, tz=pytz.utc)
+            dates = matplotlib.dates.num2date(dates)
         except:
             return _dates
 
diff --git a/packages/python/plotly/plotly/tests/test_core/test_utils/test_utils.py b/packages/python/plotly/plotly/tests/test_core/test_utils/test_utils.py
index 1587e388bdc..7a8b5ca094e 100644
--- a/packages/python/plotly/plotly/tests/test_core/test_utils/test_utils.py
+++ b/packages/python/plotly/plotly/tests/test_core/test_utils/test_utils.py
@@ -5,7 +5,7 @@
 
 import json as _json
 
-from plotly.utils import PlotlyJSONEncoder, get_by_path, memoize, node_generator
+from plotly.utils import PlotlyJSONEncoder, get_by_path, node_generator
 
 
 class TestJSONEncoder(TestCase):
@@ -48,98 +48,3 @@ def test_node_generator(self):
         ]
         for i, item in enumerate(node_generator(node0)):
             self.assertEqual(item, expected_node_path_tuples[i])
-
-
-class TestMemoizeDecorator(TestCase):
-
-    # In Python 2.x, globals should be module-scoped. By defining and
-    # instantiating a class, we *access* the global first before attempting
-    # to update a value. I.e., you *cannot* simply mutate the global value
-    # on it's own.
-    class Namespace(object):
-        pass
-
-    def test_memoize(self):
-        name_space = self.Namespace()
-        name_space.call_count = 0
-
-        @memoize()
-        def add(a, b):
-            name_space.call_count += 1
-            return a + b
-
-        tests = [[(1, 1), 2], [(2, 3), 5], [(3, -3), 0]]
-
-        self.assertEqual(name_space.call_count, 0)
-        for i, (inputs, result) in enumerate(tests, 1):
-            for _ in range(10):
-                self.assertEqual(add(*inputs), result)
-                self.assertEqual(name_space.call_count, i)
-
-    def test_memoize_maxsize(self):
-        name_space = self.Namespace()
-        name_space.call_count = 0
-
-        maxsize = 10
-
-        @memoize(maxsize=maxsize)
-        def identity(a):
-            name_space.call_count += 1
-            return a
-
-        # Function hasn't been called yet, we should get *up to* maxsize cache.
-        for i in range(maxsize):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, i + 1)
-
-        # Nothing should have been discarded yet. no additional calls.
-        for i in range(maxsize):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, maxsize)
-
-        # Make a new call...
-        self.assertEqual(identity(maxsize), maxsize)
-        self.assertEqual(name_space.call_count, maxsize + 1)
-
-        # All but the first call should be remembered.
-        for i in range(1, maxsize + 1):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, maxsize + 1)
-
-        # The *initial* call should now be forgotten for each new call.
-        for i in range(maxsize):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, maxsize + 1 + i + 1)
-
-    def test_memoize_maxsize_none(self):
-        name_space = self.Namespace()
-        name_space.call_count = 0
-
-        @memoize(maxsize=None)
-        def identity(a):
-            name_space.call_count += 1
-            return a
-
-        # Function hasn't been called yet, we should get *up to* maxsize cache.
-        for i in range(400):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, i + 1)
-
-        # Nothing should have been discarded. no additional calls.
-        for i in range(400):
-            self.assertEqual(identity(i), i)
-            self.assertEqual(name_space.call_count, 400)
-
-    def test_memoize_function_info(self):
-        # We use the decorator module to assure that function info is not
-        # overwritten by the decorator.
-
-        @memoize()
-        def foo(a, b, c="see?"):
-            """Foo is foo."""
-            pass
-
-        self.assertEqual(foo.__doc__, "Foo is foo.")
-        self.assertEqual(foo.__name__, "foo")
-        self.assertEqual(getargspec(foo).args, ["a", "b", "c"])
-        self.assertEqual(getargspec(foo).defaults, ("see?",))
diff --git a/packages/python/plotly/plotly/tests/test_optional/test_utils/test_utils.py b/packages/python/plotly/plotly/tests/test_optional/test_utils/test_utils.py
index 4027eb0b2b7..fd5f45ce54d 100644
--- a/packages/python/plotly/plotly/tests/test_optional/test_utils/test_utils.py
+++ b/packages/python/plotly/plotly/tests/test_optional/test_utils/test_utils.py
@@ -113,33 +113,23 @@ def test_encode_as_numpy(self):
         res = utils.PlotlyJSONEncoder.encode_as_numpy(np.ma.core.masked)
         self.assertTrue(math.isnan(res))
 
-    def test_encode_valid_datetime(self):
-
-        # should *fail* without 'utcoffset' and 'isoformat' and '__sub__' attrs
-        # non_datetimes = [datetime.date(2013, 10, 1), 'noon', 56, '00:00:00']
-        non_datetimes = [datetime.date(2013, 10, 1)]
-        for obj in non_datetimes:
-            self.assertRaises(
-                utils.NotEncodable, utils.PlotlyJSONEncoder.encode_as_datetime, obj
-            )
-
     def test_encode_as_datetime(self):
         # should succeed with 'utcoffset', 'isoformat' and '__sub__' attrs
         res = utils.PlotlyJSONEncoder.encode_as_datetime(datetime.datetime(2013, 10, 1))
-        self.assertEqual(res, "2013-10-01")
+        self.assertEqual(res, "2013-10-01T00:00:00")
 
     def test_encode_as_datetime_with_microsecond(self):
         # should not include extraneous microsecond info if DNE
         res = utils.PlotlyJSONEncoder.encode_as_datetime(
             datetime.datetime(2013, 10, 1, microsecond=0)
         )
-        self.assertEqual(res, "2013-10-01")
+        self.assertEqual(res, "2013-10-01T00:00:00")
 
         # should include microsecond info if present
         res = utils.PlotlyJSONEncoder.encode_as_datetime(
             datetime.datetime(2013, 10, 1, microsecond=10)
         )
-        self.assertEqual(res, "2013-10-01 00:00:00.000010")
+        self.assertEqual(res, "2013-10-01T00:00:00.000010")
 
     def test_encode_as_datetime_with_localized_tz(self):
         # should convert tzinfo to utc. Note that in october, we're in EDT!
@@ -148,7 +138,7 @@ def test_encode_as_datetime_with_localized_tz(self):
         aware_datetime = pytz.timezone("US/Eastern").localize(naive_datetime)
 
         res = utils.PlotlyJSONEncoder.encode_as_datetime(aware_datetime)
-        self.assertEqual(res, "2013-10-01 04:00:00")
+        self.assertEqual(res, "2013-10-01T00:00:00-04:00")
 
     def test_encode_as_date(self):
 
diff --git a/packages/python/plotly/plotly/utils.py b/packages/python/plotly/plotly/utils.py
index 5ce9c3765fb..bf58ff756a1 100644
--- a/packages/python/plotly/plotly/utils.py
+++ b/packages/python/plotly/plotly/utils.py
@@ -1,10 +1,8 @@
 from __future__ import absolute_import, division
 
 import textwrap
-from collections import deque
 from pprint import PrettyPrinter
 
-from decorator import decorator
 from _plotly_utils.utils import *
 
 
@@ -209,47 +207,3 @@ def decode_unicode(coll):
                     pass
             coll[str(key)] = coll.pop(key)
     return coll
-
-
-def memoize(maxsize=128):
-    """
-    Memoize a function by its arguments. Note, if the wrapped function returns
-    a mutable result, the caller is responsible for *not* mutating the result
-    as it will mutate the cache itself.
-
-    :param (int|None) maxsize: Limit the number of cached results. This is a
-                               simple way to prevent memory leaks. Setting this
-                               to `None` will remember *all* calls. The 128
-                               number is used for parity with the Python 3.2
-                               `functools.lru_cache` tool.
-
-    """
-    keys = deque()
-    cache = {}
-
-    def _memoize(*all_args, **kwargs):
-        func = all_args[0]
-        args = all_args[1:]
-        key = _default_memoize_key_function(*args, **kwargs)
-
-        if key in keys:
-            return cache[key]
-
-        if maxsize is not None and len(keys) == maxsize:
-            cache.pop(keys.pop())
-
-        result = func(*args, **kwargs)
-        keys.appendleft(key)
-        cache[key] = result
-        return result
-
-    return decorator(_memoize)
-
-
-def _default_memoize_key_function(*args, **kwargs):
-    """Factored out in case we want to allow callers to specify this func."""
-    if kwargs:
-        # frozenset is used to ensure hashability
-        return args, frozenset(kwargs.items())
-    else:
-        return args
diff --git a/packages/python/plotly/recipe/meta.yaml b/packages/python/plotly/recipe/meta.yaml
index 47cee81cd94..4c985667e69 100644
--- a/packages/python/plotly/recipe/meta.yaml
+++ b/packages/python/plotly/recipe/meta.yaml
@@ -18,13 +18,9 @@ requirements:
     - python
     - pip
     - nodejs
+    - setuptools
   run:
     - python
-    - setuptools
-    - decorator >=4.0.6
-    - nbformat >=4.2
-    - pytz
-    - requests
     - retrying >=1.3.3
     - six
 
diff --git a/packages/python/plotly/requirements.txt b/packages/python/plotly/requirements.txt
index dfb0bbe4291..496204893c7 100644
--- a/packages/python/plotly/requirements.txt
+++ b/packages/python/plotly/requirements.txt
@@ -5,14 +5,8 @@
 ###                                             ###
 ###################################################
 
-## http request dependencies ##
-requests
-
 ## python 2 to 3 compatibility ##
 six==1.8.0
 
-## timezone definitions ##
-pytz==2014.9
-
 ## retrying requests ##
 retrying==1.3.3
diff --git a/packages/python/plotly/setup.py b/packages/python/plotly/setup.py
index ff0e9b36a9b..8c628b627a7 100644
--- a/packages/python/plotly/setup.py
+++ b/packages/python/plotly/setup.py
@@ -489,14 +489,7 @@ def run(self):
         ),
         ("etc/jupyter/nbconfig/notebook.d", ["plotlywidget.json"]),
     ],
-    install_requires=[
-        "decorator>=4.0.6",
-        "nbformat>=4.2",
-        "pytz",
-        "requests",
-        "retrying>=1.3.3",
-        "six",
-    ],
+    install_requires=["retrying>=1.3.3", "six"],
     zip_safe=False,
     cmdclass=dict(
         build_py=js_prerelease(versioneer_cmds["build_py"]),