Silence warning in _determine_cmap_params

Author: spencerkclark

xarray/plot/utils.py

@@ -189,6 +189,15 @@ def _determine_cmap_params(
     else:
         mpl = attempt_import("matplotlib")
 
+    if plot_data.dtype.kind == "m":
+        unit, _ = np.datetime_data(plot_data.dtype)
+        zero = np.timedelta64(0, unit)
+    elif plot_data.dtype.kind == "M":
+        unit, _ = np.datetime_data(plot_data.dtype)
+        zero = np.datetime64(0, unit)
+    else:
+        zero = 0.0
+
     if isinstance(levels, Iterable):
         levels = sorted(levels)
 
@@ -197,15 +206,15 @@ def _determine_cmap_params(
     # Handle all-NaN input data gracefully
     if calc_data.size == 0:
         # Arbitrary default for when all values are NaN
-        calc_data = np.array(0.0)
+        calc_data = np.array(zero)
 
     # Setting center=False prevents a divergent cmap
     possibly_divergent = center is not False
 
     # Set center to 0 so math below makes sense but remember its state
     center_is_none = False
     if center is None:
-        center = 0
+        center = zero
         center_is_none = True
 
     # Setting both vmin and vmax prevents a divergent cmap
@@ -240,10 +249,10 @@ def _determine_cmap_params(
 
     if possibly_divergent:
         levels_are_divergent = (
-            isinstance(levels, Iterable) and levels[0] * levels[-1] < 0
+            isinstance(levels, Iterable) and levels[0] * levels[-1] < zero
         )
         # kwargs not specific about divergent or not: infer defaults from data
-        divergent = (vmin < 0 < vmax) or not center_is_none or levels_are_divergent
+        divergent = (vmin < zero < vmax) or not center_is_none or levels_are_divergent
     else:
         divergent = False