expose CFTimeIndex to public API (#2141)

* expose CFTimeIndex to public API

* more docs

Author: Joe Hamman

doc/api.rst

@@ -522,6 +522,13 @@ GroupByObjects
    core.groupby.DatasetGroupBy.apply
    core.groupby.DatasetGroupBy.reduce
 
+Custom Indexes
+==============
+.. autosummary::
+   :toctree: generated/
+
+   CFTimeIndex
+
 Plotting
 ========
 

xarray/__init__.py

@@ -22,6 +22,8 @@
 
 from .conventions import decode_cf, SerializationWarning
 
+from .coding.cftimeindex import CFTimeIndex
+
 try:
     from .version import version as __version__
 except ImportError:  # pragma: no cover

xarray/coding/cftimeindex.py

@@ -135,6 +135,10 @@ def assert_all_valid_date_type(data):
 
 
 class CFTimeIndex(pd.Index):
+    """Custom Index for working with CF calendars and dates
+
+    All elements of a CFTimeIndex must be cftime.datetime objects.
+    """
     year = _field_accessor('year', 'The year of the datetime')
     month = _field_accessor('month', 'The month of the datetime')
     day = _field_accessor('day', 'The days of the datetime')