Make sure datetime object arrays are converted to datetime64 (#2513)

Fixes #2512

Author: dcherian

doc/whats-new.rst

@@ -94,6 +94,9 @@ Bug fixes
 - Addition and subtraction operators used with a CFTimeIndex now preserve the
   index's type. (:issue:`2244`).
   By `Spencer Clark <https://github.com/spencerkclark>`_.
+- We now properly handle arrays of ``datetime.datetime`` and ``datetime.timedelta``
+  provided as coordinates. (:issue:`2512`)
+  By `Deepak Cherian <https://github.com/dcherian`_.
 - ``xarray.DataArray.roll`` correctly handles multidimensional arrays.
   (:issue:`2445`)
   By `Keisuke Fujii <https://github.com/fujiisoup>`_.

xarray/core/variable.py

@@ -95,7 +95,7 @@ def as_variable(obj, name=None):
                 'cannot set variable %r with %r-dimensional data '
                 'without explicit dimension names. Pass a tuple of '
                 '(dims, data) instead.' % (name, data.ndim))
-        obj = Variable(name, obj, fastpath=True)
+        obj = Variable(name, data, fastpath=True)
     else:
         raise TypeError('unable to convert object into a variable without an '
                         'explicit list of dimensions: %r' % obj)

xarray/tests/test_variable.py

@@ -992,6 +992,13 @@ def test_as_variable(self):
                 ValueError, 'has more than 1-dimension'):
             as_variable(expected, name='x')
 
+        # test datetime, timedelta conversion
+        dt = np.array([datetime(1999, 1, 1) + timedelta(days=x)
+                       for x in range(10)])
+        assert as_variable(dt, 'time').dtype.kind == 'M'
+        td = np.array([timedelta(days=x) for x in range(10)])
+        assert as_variable(td, 'time').dtype.kind == 'm'
+
     def test_repr(self):
         v = Variable(['time', 'x'], [[1, 2, 3], [4, 5, 6]], {'foo': 'bar'})
         expected = dedent("""