BUG: pandas.Timedelta min and max limits

*Problem*
Pandas Timedelta derives from `datetime.timedelta` and increases
the resolution of the timedeltas to nanoseconds. As such
Pandas.Timedelta has a smaller range of values.

*Solution*
This change modifies the advertised `min` and `max` timedeltas.

Author: has2k1

doc/source/whatsnew/v0.18.1.txt

@@ -129,6 +129,7 @@ Bug Fixes
 
 
 - Bug in ``Timestamp.__repr__`` that caused ``pprint`` to fail in nested structures (:issue:`12622`)
+- Bug in ``Timedelta.min`` and ``Timedelta.max``, the properties now report the true minimum/maximum timedeltas as recognized by Pandas. (:issue:`12727`)
 
 
 

pandas/tseries/tests/test_timedeltas.py

@@ -1083,6 +1083,35 @@ def test_timedelta_hash_equality(self):
         ns_td = Timedelta(1, 'ns')
         self.assertNotEqual(hash(ns_td), hash(ns_td.to_pytimedelta()))
 
+    def test_implementation_limits(self):
+        min_td = Timedelta(Timedelta.min)
+        max_td = Timedelta(Timedelta.max)
+
+        # GH 12727
+        # timedelta limits correspond to int64 boundaries
+        self.assertTrue(min_td.value == np.iinfo(np.int64).min + 1)
+        self.assertTrue(max_td.value == np.iinfo(np.int64).max)
+
+        # Beyond lower limit, a NAT before the Overflow
+        self.assertIsInstance(min_td - Timedelta(1, 'ns'),
+                              pd.tslib.NaTType)
+
+        with tm.assertRaises(OverflowError):
+            min_td - Timedelta(2, 'ns')
+
+        with tm.assertRaises(OverflowError):
+            max_td + Timedelta(1, 'ns')
+
+        # Same tests using the internal nanosecond values
+        td = Timedelta(min_td.value - 1, 'ns')
+        self.assertIsInstance(td, pd.tslib.NaTType)
+
+        with tm.assertRaises(OverflowError):
+            Timedelta(min_td.value - 2, 'ns')
+
+        with tm.assertRaises(OverflowError):
+            Timedelta(max_td.value + 1, 'ns')
+
 
 class TestTimedeltaIndex(tm.TestCase):
     _multiprocess_can_split_ = True

pandas/tslib.pyx

@@ -2722,6 +2722,11 @@ class Timedelta(_Timedelta):
     __pos__ = _op_unary_method(lambda x: x, '__pos__')
     __abs__ = _op_unary_method(lambda x: abs(x), '__abs__')
 
+
+# Resolution is in nanoseconds
+Timedelta.min = Timedelta(np.iinfo(np.int64).min+1, 'ns')
+Timedelta.max = Timedelta(np.iinfo(np.int64).max, 'ns')
+
 cdef PyTypeObject* td_type = <PyTypeObject*> Timedelta
 
 cdef inline bint is_timedelta(object o):