Remove registration of pandas datetime converter in plotting (pydata#6109)

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

doc/whats-new.rst

@@ -29,6 +29,8 @@ New Features
 
 Breaking changes
 ~~~~~~~~~~~~~~~~
+- Rely on matplotlib's default datetime converters instead of pandas' (:issue:`6102`, :pull:`6109`).
+  By `Jimmy Westling <https://github.com/illviljan>`_.
 - Improve repr readability when there are a large number of dimensions in datasets or dataarrays by
   wrapping the text once the maximum display width has been exceeded. (:issue: `5546`, :pull:`5662`)
   By `Jimmy Westling <https://github.com/illviljan>`_.

xarray/plot/utils.py

@@ -28,20 +28,9 @@
 ROBUST_PERCENTILE = 2.0
 
 
-_registered = False
-
-
-def register_pandas_datetime_converter_if_needed():
-    # based on https://github.com/pandas-dev/pandas/pull/17710
-    global _registered
-    if not _registered:
-        pd.plotting.register_matplotlib_converters()
-        _registered = True
-
-
 def import_matplotlib_pyplot():
-    """Import pyplot as register appropriate converters."""
-    register_pandas_datetime_converter_if_needed()
+    """import pyplot"""
+    # TODO: This function doesn't do anything (after #6109), remove it?
     import matplotlib.pyplot as plt
 
     return plt

xarray/tests/test_plot.py

@@ -2674,7 +2674,37 @@ def test_datetime_units(self):
         # test that matplotlib-native datetime works:
         fig, ax = plt.subplots()
         ax.plot(self.darray["time"], self.darray)
-        assert isinstance(ax.xaxis.get_major_locator(), mpl.dates.AutoDateLocator)
+
+        # Make sure only mpl converters are used, use type() so only
+        # mpl.dates.AutoDateLocator passes and no other subclasses:
+        assert type(ax.xaxis.get_major_locator()) is mpl.dates.AutoDateLocator
+
+    def test_datetime_plot1d(self):
+        # Test that matplotlib-native datetime works:
+        p = self.darray.plot.line()
+        ax = p[0].axes
+
+        # Make sure only mpl converters are used, use type() so only
+        # mpl.dates.AutoDateLocator passes and no other subclasses:
+        assert type(ax.xaxis.get_major_locator()) is mpl.dates.AutoDateLocator
+
+    def test_datetime_plot2d(self):
+        # Test that matplotlib-native datetime works:
+        da = DataArray(
+            np.arange(3 * 4).reshape(3, 4),
+            dims=("x", "y"),
+            coords={
+                "x": [1, 2, 3],
+                "y": [np.datetime64(f"2000-01-{x:02d}") for x in range(1, 5)],
+            },
+        )
+
+        p = da.plot.pcolormesh()
+        ax = p.axes
+
+        # Make sure only mpl converters are used, use type() so only
+        # mpl.dates.AutoDateLocator passes and no other subclasses:
+        assert type(ax.xaxis.get_major_locator()) is mpl.dates.AutoDateLocator
 
 
 @pytest.mark.filterwarnings("ignore:setting an array element with a sequence")