diff --git a/pandas/plotting/_matplotlib/converter.py b/pandas/plotting/_matplotlib/converter.py
index 05377e0c240b9..1ce727749c1e6 100644
--- a/pandas/plotting/_matplotlib/converter.py
+++ b/pandas/plotting/_matplotlib/converter.py
@@ -252,11 +252,7 @@ def _dt_to_float_ordinal(dt):
     preserving hours, minutes, seconds and microseconds.  Return value
     is a :func:`float`.
     """
-    if isinstance(dt, (np.ndarray, Index, Series)) and is_datetime64_ns_dtype(dt):
-        base = dates.epoch2num(dt.asi8 / 1.0e9)
-    else:
-        base = dates.date2num(dt)
-    return base
+    return dates.date2num(dt)
 
 
 # Datetime Conversion