From 0af882ae157a6ef52bda6ea15ba4c8fb10f5d5b8 Mon Sep 17 00:00:00 2001
From: Alex Kleeman <kleeman@climate.com>
Date: Sun, 2 Mar 2014 23:14:35 -0800
Subject: [PATCH 1/2] During decode_cf do not encode any 'object' dtypes.

When encoding cf variables check if dtype is np.datetime64.

fixes akleeman/xray/issues/39
---
 src/xray/conventions.py | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/xray/conventions.py b/src/xray/conventions.py
index 773bd5bf188..0f5a0b2fa2f 100644
--- a/src/xray/conventions.py
+++ b/src/xray/conventions.py
@@ -249,11 +249,12 @@ def encode_cf_variable(array):
     attributes = array.attributes.copy()
     encoding = array.encoding
 
-    if isinstance(data, pd.DatetimeIndex):
+    if (isinstance(data, pd.DatetimeIndex) or
+        str(data.dtype).startswith('datetime')):
         # DatetimeIndex objects need to be encoded into numeric arrays
         (data, units, calendar) = utils.datetimeindex2num(data,
-                                          units=encoding.get('units', None),
-                                          calendar=encoding.get('calendar', None))
+                                          units=encoding.pop('units', None),
+                                          calendar=encoding.pop('calendar', None))
         attributes['units'] = units
         attributes['calendar'] = calendar
     elif data.dtype == np.dtype('O'):
@@ -327,7 +328,10 @@ def pop_to(source, dest, k):
     if 'dtype' in encoding:
         if var.data.dtype != encoding['dtype']:
             raise ValueError("Refused to overwrite dtype")
-    encoding['dtype'] = data.dtype
+    if not isinstance(data, pd.Index):
+        # When data is a pandas Index we assume the dtype will be
+        # inferred during encode_cf_variable.
+        encoding['dtype'] = data.dtype
     if np.issubdtype(data.dtype, (str, unicode)):
         # TODO: add some sort of check instead of just assuming that the last
         # dimension on a character array is always the string dimension

From 34b65e1af60b1740dd825b47ff80a0e50d0ade64 Mon Sep 17 00:00:00 2001
From: akleeman <akleeman@gmail.com>
Date: Sun, 2 Mar 2014 23:52:14 -0800
Subject: [PATCH 2/2] Update conventions.py

Changed datetime check, copied encoding.
---
 src/xray/conventions.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/xray/conventions.py b/src/xray/conventions.py
index 0f5a0b2fa2f..e7df7b5785c 100644
--- a/src/xray/conventions.py
+++ b/src/xray/conventions.py
@@ -247,10 +247,9 @@ def encode_cf_variable(array):
     dimensions = array.dimensions
     data = array.data
     attributes = array.attributes.copy()
-    encoding = array.encoding
+    encoding = array.encoding.copy()
 
-    if (isinstance(data, pd.DatetimeIndex) or
-        str(data.dtype).startswith('datetime')):
+    if np.issubdtype(data.dtype, np.datetime64):
         # DatetimeIndex objects need to be encoded into numeric arrays
         (data, units, calendar) = utils.datetimeindex2num(data,
                                           units=encoding.pop('units', None),