Didn't realize that _to_ordinalf needs to support datetime.date objects.

pganssle · pganssle · commit 9f66ae2530d0 · 2014-12-25T14:34:57.000-06:00
Signed-off-by: Paul G &lt;p.ganssle@gmail.com&gt;
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -205,11 +205,14 @@ def _get_rc_timezone():
 
 def _to_ordinalf(dt):
     """
-    Convert :mod:`datetime` to the Gregorian date as UTC float days,
-    preserving hours, minutes, seconds and microseconds.  Return value
+    Convert :mod:`datetime` or :mod:`date` to the Gregorian date as UTC float 
+    days, preserving hours, minutes, seconds and microseconds.  Return value
     is a :func:`float`.
     """
 
+    if isinstance(dt, datetime.date):
+        return float(datetime.datetime.toordinal(dt))
+
     if hasattr(dt, 'tzinfo') and dt.tzinfo is not None:
         delta = dt.tzinfo.utcoffset(dt)
         if delta is not None:
