Fix problem with inconsistent time zones. This now also fixes Issue #3896.

pganssle · pganssle · commit ba623a78f540 · 2014-12-24T21:17:35.000-06:00
Signed-off-by: Paul G &lt;p.ganssle@gmail.com&gt;
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -215,12 +215,16 @@ def _to_ordinalf(dt):
         if delta is not None:
             dt -= delta
 
-    base = dt.toordinal()
-    td_remainder = (dt-datetime.datetime.fromordinal(base)).total_seconds()
+    # Get a datetime object at midnight in the same time zone as dt.
+    cdate = dt.date()
+    midnight_time = datetime.time(0, 0, 0, tzinfo=dt.tzinfo)
 
-    base = float(base)
+    rdt = datetime.datetime.combine(cdate, midnight_time)
+    td_remainder = (dt-rdt).total_seconds()
+
+    base = float(dt.toordinal())
     if td_remainder > 0:
-        base ++ td_remainder / SEC_PER_DAY
+        base += td_remainder / SEC_PER_DAY
 
     return base
 
