diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index 7f7290c6e502..786b8892b8d4 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -3926,6 +3926,10 @@ def dopatch(xs, ys, **kwargs):
         elif len(positions) != N:
             raise ValueError(datashape_message.format("positions"))
 
+        positions = np.array(positions)
+        if len(positions) > 0 and not isinstance(positions[0], Number):
+            raise TypeError("positions should be an iterable of numbers")
+
         # width
         if widths is None:
             widths = [np.clip(0.15 * np.ptp(positions), 0.15, 0.5)] * N
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index 40c23f6c5967..2dbb3c2fba6c 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -1524,6 +1524,15 @@ def test_bar_timedelta():
                    (10, 20))
 
 
+def test_boxplot_dates_pandas(pd):
+    # smoke test for boxplot and dates in pandas
+    data = np.random.rand(5, 2)
+    years = pd.date_range('1/1/2000',
+                          periods=2, freq=pd.DateOffset(years=1)).year
+    plt.figure()
+    plt.boxplot(data, positions=years)
+
+
 def test_bar_pandas(pd):
     # Smoke test for pandas