diff --git a/pandas/_libs/reduction.pyx b/pandas/_libs/reduction.pyx
index fe993ecc0cdd7..fdcb41da46303 100644
--- a/pandas/_libs/reduction.pyx
+++ b/pandas/_libs/reduction.pyx
@@ -18,8 +18,6 @@ cnp.import_array()
 cimport util
 from lib import maybe_convert_objects
 
-is_numpy_prior_1_6_2 = LooseVersion(np.__version__) < '1.6.2'
-
 
 cdef _get_result_array(object obj, Py_ssize_t size, Py_ssize_t cnt):
 
diff --git a/pandas/_libs/tslib.pyx b/pandas/_libs/tslib.pyx
index be695eabb24bd..bdd279b19208b 100644
--- a/pandas/_libs/tslib.pyx
+++ b/pandas/_libs/tslib.pyx
@@ -46,8 +46,7 @@ from tslibs.nattype cimport checknull_with_nat, NPY_NAT
 
 from tslibs.offsets cimport to_offset
 
-from tslibs.timestamps cimport (create_timestamp_from_ts,
-                                _NS_UPPER_BOUND, _NS_LOWER_BOUND)
+from tslibs.timestamps cimport create_timestamp_from_ts
 from tslibs.timestamps import Timestamp
 
 
@@ -350,8 +349,8 @@ cpdef array_with_unit_to_datetime(ndarray values, unit, errors='coerce'):
         # check the bounds
         if not need_to_iterate:
 
-            if ((fvalues < _NS_LOWER_BOUND).any()
-                    or (fvalues > _NS_UPPER_BOUND).any()):
+            if ((fvalues < Timestamp.min.value).any()
+                    or (fvalues > Timestamp.max.value).any()):
                 raise OutOfBoundsDatetime("cannot convert input with unit "
                                           "'{unit}'".format(unit=unit))
             result = (iresult * m).astype('M8[ns]')
diff --git a/pandas/_libs/tslibs/timestamps.pxd b/pandas/_libs/tslibs/timestamps.pxd
index d6b649becc479..a162799828cba 100644
--- a/pandas/_libs/tslibs/timestamps.pxd
+++ b/pandas/_libs/tslibs/timestamps.pxd
@@ -6,5 +6,3 @@ from np_datetime cimport npy_datetimestruct
 cdef object create_timestamp_from_ts(int64_t value,
                                      npy_datetimestruct dts,
                                      object tz, object freq)
-
-cdef int64_t _NS_UPPER_BOUND, _NS_LOWER_BOUND