rcomer · Jan 25, 2026 · Nov 16, 2025 · Nov 16, 2025 · Nov 16, 2025 · Nov 29, 2025
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -2,6 +2,7 @@
 import itertools
 import logging
 import math
+import datetime
 from numbers import Integral, Number, Real
 
 import re
@@ -9057,6 +9058,19 @@ def violin(self, vpstats, positions=None, vert=None,
         elif len(widths) != N:
             raise ValueError(datashape_message.format("widths"))
 
+        # For usability / better error message:
+        # Validate that datetime-like positions have timedelta-like widths.
+        # Checking only the first element is good enough for standard misuse cases
+        pos0 = positions[0]
+        width0 = widths if np.isscalar(widths) else widths[0]
+        if (isinstance(pos0, (datetime.datetime, datetime.date))
+                and not isinstance(width0, datetime.timedelta)):
+            raise TypeError(
+                "datetime/date 'position' values, require timedelta 'widths'")
+        elif (isinstance(pos0, np.datetime64)
+                and not isinstance(width0, np.timedelta64)):
+            raise TypeError(
+                "np.datetime64 'position' values, require np.timedelta64 'widths'")
         # Validate side
         _api.check_in_list(["both", "low", "high"], side=side)
 

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4121,6 +4121,81 @@ def test_violinplot_sides():
                       showextrema=True, showmedians=True, side=side)
 
 
+def violin_plot_stats():
+    datetimes = [
+        datetime.datetime(2023, 2, 10),
+        datetime.datetime(2023, 5, 18),
+        datetime.datetime(2023, 6, 6)
+    ]
+    return [{
+        'coords': datetimes,
+        'vals': [1.2, 2.8, 1.5],
+        'mean': 1.84,
+        'median': 1.5,
+        'min': 1.2,
+        'max': 2.8,
+        'quantiles': [1.2, 1.5, 2.8]
+    }, {
+        'coords': datetimes,
+        'vals': [0.8, 1.1, 0.9],
+        'mean': 0.94,
+        'median': 0.9,
+        'min': 0.8,
+        'max': 1.1,
+        'quantiles': [0.8, 0.9, 1.1]
+    }]
+
+
+def test_datetime_positions_with_datetime64():
+    """Test that datetime positions with float widths raise TypeError."""
+    fig, ax = plt.subplots()
+    positions = [np.datetime64('2020-01-01'), np.datetime64('2021-01-01')]
+    widths = [0.5, 1.0]
+    with pytest.raises(TypeError,
+    match="np.datetime64 'position' values, require np.timedelta64 'widths'"):
+        ax.violin(violin_plot_stats(), positions=positions, widths=widths)
+
+
+def test_datetime_positions_with_float_widths_raises():
+    """Test that datetime positions with float widths raise TypeError."""
+    fig, ax = plt.subplots()
+    positions = [datetime.datetime(2020, 1, 1), datetime.datetime(2021, 1, 1)]
+    widths = [0.5, 1.0]
+    with pytest.raises(TypeError,
+    match="datetime/date 'position' values, require timedelta 'widths'"):
+        ax.violin(violin_plot_stats(), positions=positions, widths=widths)
+
+
+def test_datetime_positions_with_scalar_float_width_raises():
+    """Test that datetime positions with scalar float width raise TypeError."""
+    fig, ax = plt.subplots()
+    positions = [datetime.datetime(2020, 1, 1), datetime.datetime(2021, 1, 1)]
+    widths = 0.75
+    with pytest.raises(TypeError,
+    match="datetime/date 'position' values, require timedelta 'widths'"):
+        ax.violin(violin_plot_stats(), positions=positions, widths=widths)
+
+
+def test_numeric_positions_with_float_widths_ok():
+    """Test that numeric positions with float widths work."""
+    fig, ax = plt.subplots()
+    positions = [1.0, 2.0]
+    widths = [0.5, 1.0]
+    ax.violin(violin_plot_stats(), positions=positions, widths=widths)
+
+
+def test_mixed_positions_datetime_and_numeric_behaves():
+    """Test that mixed datetime and numeric positions
+    with float widths raise TypeError.
+    """
+    fig, ax = plt.subplots()
+    positions = [datetime.datetime(2020, 1, 1), 2.0]
+    widths = [0.5, 1.0]
+    with pytest.raises(TypeError,
+    match="datetime/date 'position' values, require timedelta 'widths'"):
+        ax.violin(violin_plot_stats(), positions=positions, widths=widths)
+
+
 def test_violinplot_bad_positions():
     ax = plt.axes()
     # First 9 digits of frac(sqrt(47))