Default to UTC in the legacy date parser.

src/dateparser-inl.h

Index: src/dateparser-inl.h
diff --git a/src/dateparser-inl.h b/src/dateparser-inl.h
index 3cb36fa433998e96dbb9acadae999a791cc89277..4f74a088bd924ec1ea829cc06fa9aa57b48e4efb 100644
--- a/src/dateparser-inl.h
+++ b/src/dateparser-inl.h
@@ -178,7 +178,8 @@ bool DateParser::Parse(Vector<Char> str,
       // Ignore other characters and whitespace.
     }
   }
-
+  // Successfully parsed ES5 Date Time String. Default to UTC if no TZ given.
+  if (tz.IsEmpty()) tz.Set(0);
   return day.Write(out) && time.Write(out) && tz.Write(out);
 }