Deprecate certain cftime frequency strings following pandas

doc/user-guide/time-series.rst

@@ -89,7 +89,7 @@ items and with the `slice` object:
 
 .. ipython:: python
 
-    time = pd.date_range("2000-01-01", freq="H", periods=365 * 24)
+    time = pd.date_range("2000-01-01", freq="h", periods=365 * 24)
     ds = xr.Dataset({"foo": ("time", np.arange(365 * 24)), "time": time})
     ds.sel(time="2000-01")
     ds.sel(time=slice("2000-06-01", "2000-06-10"))
@@ -115,7 +115,7 @@ given ``DataArray`` can be quickly computed using a special ``.dt`` accessor.
 
 .. ipython:: python
 
-    time = pd.date_range("2000-01-01", freq="6H", periods=365 * 4)
+    time = pd.date_range("2000-01-01", freq="6h", periods=365 * 4)
     ds = xr.Dataset({"foo": ("time", np.arange(365 * 4)), "time": time})
     ds.time.dt.hour
     ds.time.dt.dayofweek
@@ -207,7 +207,7 @@ For example, we can downsample our dataset from hourly to 6-hourly:
 .. ipython:: python
     :okwarning:
 
-    ds.resample(time="6H")
+    ds.resample(time="6h")
 
 This will create a specialized ``Resample`` object which saves information
 necessary for resampling. All of the reduction methods which work with
@@ -216,21 +216,21 @@ necessary for resampling. All of the reduction methods which work with
 .. ipython:: python
     :okwarning:
 
-    ds.resample(time="6H").mean()
+    ds.resample(time="6h").mean()
 
 You can also supply an arbitrary reduction function to aggregate over each
 resampling group:
 
 .. ipython:: python
 
-    ds.resample(time="6H").reduce(np.mean)
+    ds.resample(time="6h").reduce(np.mean)
 
 You can also resample on the time dimension while applying reducing along other dimensions at the same time
 by specifying the `dim` keyword argument
 
 .. code-block:: python
 
-    ds.resample(time="6H").mean(dim=["time", "latitude", "longitude"])
+    ds.resample(time="6h").mean(dim=["time", "latitude", "longitude"])
 
 For upsampling, xarray provides six methods: ``asfreq``, ``ffill``, ``bfill``, ``pad``,
 ``nearest`` and ``interpolate``. ``interpolate`` extends ``scipy.interpolate.interp1d``
@@ -243,7 +243,7 @@ Data that has indices outside of the given ``tolerance`` are set to ``NaN``.
 
 .. ipython:: python
 
-    ds.resample(time="1H").nearest(tolerance="1H")
+    ds.resample(time="1h").nearest(tolerance="1h")
 
 
 For more examples of using grouped operations on a time dimension, see

doc/user-guide/weather-climate.rst

@@ -239,7 +239,7 @@ For data indexed by a :py:class:`~xarray.CFTimeIndex` xarray currently supports:
 
 .. ipython:: python
 
-    da.resample(time="81T", closed="right", label="right", offset="3T").mean()
+    da.resample(time="81min", closed="right", label="right", offset="3min").mean()
 
 .. _nanosecond-precision range: https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html#timestamp-limitations
 .. _ISO 8601 standard: https://en.wikipedia.org/wiki/ISO_8601

doc/whats-new.rst

@@ -28,6 +28,12 @@ New Features
 Breaking changes
 ~~~~~~~~~~~~~~~~
 
+- Following pandas, :py:meth:`infer_freq` will return ``"Y"``, ``"YS"``,
+  ``"QE"``, ``"ME"``, ``"h"``, ``"min"``, ``"s"``, ``"ms"``, ``"us"``, or
+  ``"ns"`` instead of ``"A"``, ``"AS"``, ``"Q"``, ``"M"``, ``"H"``, ``"T"``,
+  ``"S"``, ``"L"``, ``"U"``, or ``"N"``.  This is to be consistent with the
+  deprecation of the latter frequency strings (:issue:`8394`, :pull:`8415`). By
+  `Spencer Clark <https://github.com/spencerkclark>`_.
 
 Deprecations
 ~~~~~~~~~~~~
@@ -39,6 +45,14 @@ Deprecations
   this was one place in the API where dimension positions were used.
   (:pull:`8341`)
   By `Maximilian Roos <https://github.com/max-sixty>`_.
+- Following pandas, the frequency strings ``"A"``, ``"AS"``, ``"Q"``, ``"M"``,
+  ``"H"``, ``"T"``, ``"S"``, ``"L"``, ``"U"``, and ``"N"`` are deprecated in
+  favor of ``"Y"``, ``"YS"``, ``"QE"``, ``"ME"``, ``"h"``, ``"min"``, ``"s"``,
+  ``"ms"``, ``"us"``, and ``"ns"``, respectively.  These strings are used, for
+  example, in :py:func:`date_range`, :py:func:`cftime_range`,
+  :py:meth:`DataArray.resample`, and :py:meth:`Dataset.resample` among others
+  (:issue:`8394`, :pull:`8415`).  By `Spencer Clark
+  <https://github.com/spencerkclark>`_.
 
 Bug fixes
 ~~~~~~~~~