infer_freq: return 'YE' (#8629 follow-up) (#8642)

* infer_freq: return 'YE' (#8629 follow-up)

* fix whats new

---------

Co-authored-by: Maximilian Roos <[email protected]>

Author: mathause

doc/whats-new.rst

@@ -28,7 +28,7 @@ Breaking changes
 
 - Following pandas, :py:meth:`infer_freq` will return ``"YE"``, instead of ``"Y"`` (formerly ``"A"``).
   This is to be consistent with the deprecation of the latter frequency string in pandas 2.2.
-  This is a follow up to :pull:`8415` (:issue:`8612`, :pull:`8629`).
+  This is a follow up to :pull:`8415` (:issue:`8612`, :pull:`8642`).
   By `Mathias Hauser <https://github.com/mathause>`_.
 
 Deprecations

xarray/coding/frequencies.py

@@ -183,7 +183,7 @@ def _get_annual_rule(self):
         if len(np.unique(self.index.month)) > 1:
             return None
 
-        return {"cs": "YS", "ce": "Y"}.get(month_anchor_check(self.index))
+        return {"cs": "YS", "ce": "YE"}.get(month_anchor_check(self.index))
 
     def _get_quartely_rule(self):
         if len(self.month_deltas) > 1:

xarray/tests/test_cftimeindex.py

@@ -1353,7 +1353,7 @@ def test_infer_freq_invalid_inputs():
     "freq",
     [
         "300YS-JAN",
-        "Y-DEC",
+        "YE-DEC",
         "YS-JUL",
         "2YS-FEB",
         "QE-NOV",