diff --git a/notebook/services/contents/tz.py b/notebook/_tz.py
similarity index 100%
rename from notebook/services/contents/tz.py
rename to notebook/_tz.py
diff --git a/notebook/services/contents/filecheckpoints.py b/notebook/services/contents/filecheckpoints.py
index 46e32eadc..1cf83cfe0 100644
--- a/notebook/services/contents/filecheckpoints.py
+++ b/notebook/services/contents/filecheckpoints.py
@@ -12,11 +12,12 @@ from .checkpoints import (
 )
 from .fileio import FileManagerMixin
 
-from . import tz
 from ipython_genutils.path import ensure_dir_exists
 from ipython_genutils.py3compat import getcwd
 from traitlets import Unicode
 
+from notebook import _tz as tz
+
 
 class FileCheckpoints(FileManagerMixin, Checkpoints):
     """
diff --git a/notebook/services/contents/filemanager.py b/notebook/services/contents/filemanager.py
index cd8634313..d978d553f 100644
--- a/notebook/services/contents/filemanager.py
+++ b/notebook/services/contents/filemanager.py
@@ -22,7 +22,8 @@ from .manager import ContentsManager
 from ipython_genutils.importstring import import_item
 from traitlets import Any, Unicode, Bool, TraitError, observe, default, validate
 from ipython_genutils.py3compat import getcwd, string_types
-from . import tz
+
+from notebook import _tz as tz
 from notebook.utils import (
     is_hidden, is_file_hidden,
     to_api_path,
diff --git a/notebook/services/kernels/kernelmanager.py b/notebook/services/kernels/kernelmanager.py
index e561d3983..b5c4c9f5d 100644
--- a/notebook/services/kernels/kernelmanager.py
+++ b/notebook/services/kernels/kernelmanager.py
@@ -17,7 +17,7 @@ from jupyter_client.multikernelmanager import MultiKernelManager
 from traitlets import Dict, List, Unicode, TraitError, default, validate
 
 from notebook.utils import to_os_path
-from notebook.services.contents.tz import utcnow, isoformat
+from notebook._tz import utcnow, isoformat
 from ipython_genutils.py3compat import getcwd
 
 
diff --git a/notebook/services/sessions/tests/test_sessionmanager.py b/notebook/services/sessions/tests/test_sessionmanager.py
index 860cf4a92..96847a868 100644
--- a/notebook/services/sessions/tests/test_sessionmanager.py
+++ b/notebook/services/sessions/tests/test_sessionmanager.py
@@ -9,7 +9,7 @@ from tornado.ioloop import IOLoop
 from ..sessionmanager import SessionManager
 from notebook.services.kernels.kernelmanager import MappingKernelManager
 from notebook.services.contents.manager import ContentsManager
-from notebook.services.contents.tz import utcnow, isoformat
+from notebook._tz import utcnow, isoformat
 
 class DummyKernel(object):
     def __init__(self, kernel_name='python'):