diff --git a/pandas/_libs/tslibs/timezones.pxd b/pandas/_libs/tslibs/timezones.pxd
index e5d1343e1c984..95e0474b3a174 100644
--- a/pandas/_libs/tslibs/timezones.pxd
+++ b/pandas/_libs/tslibs/timezones.pxd
@@ -1,8 +1,6 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
 
-from numpy cimport ndarray
-
 cdef bint is_utc(object tz)
 cdef bint is_tzlocal(object tz)
 
diff --git a/pandas/_libs/tslibs/timezones.pyx b/pandas/_libs/tslibs/timezones.pyx
index 48d82996a0bd0..7f778dde86e23 100644
--- a/pandas/_libs/tslibs/timezones.pyx
+++ b/pandas/_libs/tslibs/timezones.pyx
@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
+# cython: linetrace=False
+# distutils: define_macros=CYTHON_TRACE=0
+# distutils: define_macros=CYTHON_TRACE_NOGIL=0
 
 cimport cython
 from cython cimport Py_ssize_t
@@ -275,3 +278,19 @@ cdef object get_dst_info(object tz):
         dst_cache[cache_key] = (trans, deltas, typ)
 
     return dst_cache[cache_key]
+
+
+def infer_tzinfo(start, end):
+    if start is not None and end is not None:
+        tz = start.tzinfo
+        if end.tzinfo:
+            if not (get_timezone(tz) == get_timezone(end.tzinfo)):
+                msg = 'Inputs must both have the same timezone, {tz1} != {tz2}'
+                raise AssertionError(msg.format(tz1=tz, tz2=end.tzinfo))
+    elif start is not None:
+        tz = start.tzinfo
+    elif end is not None:
+        tz = end.tzinfo
+    else:
+        tz = None
+    return tz
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 39dc24642235b..9127864eab8a1 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -443,7 +443,7 @@ def _generate(cls, start, end, periods, name, offset,
             raise ValueError("Closed has to be either 'left', 'right' or None")
 
         try:
-            inferred_tz = tools._infer_tzinfo(start, end)
+            inferred_tz = timezones.infer_tzinfo(start, end)
         except:
             raise TypeError('Start and end cannot both be tz-aware with '
                             'different timezones')
diff --git a/pandas/core/tools/datetimes.py b/pandas/core/tools/datetimes.py
index 8fe28aa400613..e335dfe3a4142 100644
--- a/pandas/core/tools/datetimes.py
+++ b/pandas/core/tools/datetimes.py
@@ -4,7 +4,6 @@
 
 from pandas._libs import tslib
 from pandas._libs.tslibs.strptime import array_strptime
-from pandas._libs.tslibs.timezones import get_timezone
 from pandas._libs.tslibs import parsing
 from pandas._libs.tslibs.parsing import (  # noqa
     parse_time_string,
@@ -30,24 +29,6 @@
 from pandas.core import algorithms
 
 
-def _infer_tzinfo(start, end):
-    def _infer(a, b):
-        tz = a.tzinfo
-        if b and b.tzinfo:
-            if not (get_timezone(tz) == get_timezone(b.tzinfo)):
-                raise AssertionError('Inputs must both have the same timezone,'
-                                     ' {timezone1} != {timezone2}'
-                                     .format(timezone1=tz, timezone2=b.tzinfo))
-        return tz
-
-    tz = None
-    if start is not None:
-        tz = _infer(start, end)
-    elif end is not None:
-        tz = _infer(end, start)
-    return tz
-
-
 def _guess_datetime_format_for_array(arr, **kwargs):
     # Try to guess the format based on the first non-NaN element
     non_nan_elements = notna(arr).nonzero()[0]
diff --git a/pandas/tests/tseries/test_timezones.py b/pandas/tests/tseries/test_timezones.py
index e7b470e01e2af..aa8fe90ea6500 100644
--- a/pandas/tests/tseries/test_timezones.py
+++ b/pandas/tests/tseries/test_timezones.py
@@ -12,7 +12,6 @@
 from datetime import datetime, timedelta, tzinfo, date
 
 import pandas.util.testing as tm
-import pandas.core.tools.datetimes as tools
 import pandas.tseries.offsets as offsets
 from pandas.compat import lrange, zip
 from pandas.core.indexes.datetimes import bdate_range, date_range
@@ -646,20 +645,20 @@ def test_infer_tz(self):
 
         start = self.localize(eastern, _start)
         end = self.localize(eastern, _end)
-        assert (tools._infer_tzinfo(start, end) is self.localize(
-            eastern, _start).tzinfo)
-        assert (tools._infer_tzinfo(start, None) is self.localize(
-            eastern, _start).tzinfo)
-        assert (tools._infer_tzinfo(None, end) is self.localize(eastern,
-                                                                _end).tzinfo)
+        assert (timezones.infer_tzinfo(start, end) is
+                self.localize(eastern, _start).tzinfo)
+        assert (timezones.infer_tzinfo(start, None) is
+                self.localize(eastern, _start).tzinfo)
+        assert (timezones.infer_tzinfo(None, end) is
+                self.localize(eastern, _end).tzinfo)
 
         start = utc.localize(_start)
         end = utc.localize(_end)
-        assert (tools._infer_tzinfo(start, end) is utc)
+        assert (timezones.infer_tzinfo(start, end) is utc)
 
         end = self.localize(eastern, _end)
-        pytest.raises(Exception, tools._infer_tzinfo, start, end)
-        pytest.raises(Exception, tools._infer_tzinfo, end, start)
+        pytest.raises(Exception, timezones.infer_tzinfo, start, end)
+        pytest.raises(Exception, timezones.infer_tzinfo, end, start)
 
     def test_tz_string(self):
         result = date_range('1/1/2000', periods=10,