CLN: Worked on Code Reveiew

Author: sumitbinnani

doc/source/whatsnew/v0.19.0.txt

@@ -24,15 +24,16 @@ New features
 
 .. _whatsnew_0190.dev_api:
 
-to_datetime can be used with Offset
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-``pd.to_datetime`` has a new parameter, ``origin``, to define an offset for ``DatetimeIndex``.
+to_datetime has gained an origin kwarg
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+``pd.to_datetime`` has a new parameter, ``origin``, to define reference date for ``DatetimeIndex``.
 
 .. ipython:: python
 
    to_datetime([1,2,3], unit='D', origin=pd.Timestamp('1960-01-01'))
 
-The above code would return days with offset from origin as defined by timestamp set by origin.
+The above code would parse the numeric values as number of days (unit='D')
+since origin as reference date.
 
 pandas development API
 ^^^^^^^^^^^^^^^^^^^^^^

pandas/tseries/tests/test_timeseries.py

@@ -796,7 +796,7 @@ def test_to_datetime_origin(self):
         epoch_timestamp_convertible = [epoch_1960, epoch_1960.to_datetime(),
                                        epoch_1960.to_datetime64(),
                                        str(epoch_1960)]
-        invalid_origins = ['random_string', '13-24-1990']
+        invalid_origins = ['random_string', '13-24-1990', '0001-01-01']
         units_from_epoch = [0, 1, 2, 3, 4]
 
         for unit in units:

pandas/tseries/tools.py

@@ -425,11 +425,15 @@ def _convert_listlike(arg, box, format, name=None, tz=tz):
             except (ValueError, TypeError):
                 raise e
 
-    def result_without_offset(arg):
+    def intermediate_result(arg):
         if origin == 'julian':
             if unit != 'D':
                 raise ValueError("unit must be 'D' for origin='julian'")
-            arg = arg - tslib.Timestamp(0).to_julian_date()
+            try:
+                arg = arg - tslib.Timestamp(0).to_julian_date()
+            except:
+                raise ValueError("incompatible 'arg' type for given "
+                                 "'origin'='julian'")
         if arg is None:
             return arg
         elif isinstance(arg, tslib.Timestamp):
@@ -446,10 +450,10 @@ def result_without_offset(arg):
             return _convert_listlike(arg, box, format)
         return _convert_listlike(np.array([arg]), box, format)[0]
 
-    result = result_without_offset(arg)
+    result = intermediate_result(arg)
 
     offset = None
-    if origin != 'epoch' and origin != 'julian':
+    if origin not in ['epoch','julian']:
         try:
             offset = tslib.Timestamp(origin) - tslib.Timestamp(0)
         except ValueError: