diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
index bd27bef3759a..ac79c441ab9a 100644
--- a/lib/matplotlib/dates.py
+++ b/lib/matplotlib/dates.py
@@ -207,9 +207,9 @@ def _get_rc_timezone():
 
 def _to_ordinalf(dt):
     """
-    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`.
+    Convert :mod:`datetime`, :mod:`date` or :mod:`timedelta` to the Gregorian
+    date as UTC float days, preserving hours, minutes, seconds and
+    microseconds. Return value is a :func:`float`.
     """
     # Convert to UTC
     tzi = getattr(dt, 'tzinfo', None)
@@ -217,6 +217,9 @@ def _to_ordinalf(dt):
         dt = dt.astimezone(UTC)
         tzi = UTC
 
+    if isinstance(dt, datetime.timedelta):
+        return dt.total_seconds() / SEC_PER_DAY
+
     base = float(dt.toordinal())
 
     # If it's sufficiently datetime-like, it will have a `date()` method
diff --git a/lib/matplotlib/tests/test_dates.py b/lib/matplotlib/tests/test_dates.py
index 5a25e6182b7e..003789951598 100644
--- a/lib/matplotlib/tests/test_dates.py
+++ b/lib/matplotlib/tests/test_dates.py
@@ -466,3 +466,10 @@ def test_tz_utc():
 def test_num2timedelta(x, tdelta):
     dt = mdates.num2timedelta(x)
     assert dt == tdelta
+
+
+def test_timedelta_ordinalf():
+    # Check that timedeltas can be converted to ordinalfs
+    dt = datetime.timedelta(seconds=60)
+    ordinalf = mdates._to_ordinalf(dt)
+    assert ordinalf == 1 / (24 * 60)