[date] Date parser says true even for wrong dates, check twice.

src/builtins.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 2078 matching lines @@
     result = DateParser::Parse(str_content.ToUC16Vector(), *tmp,
                                isolate->unicode_cache());
   }
   if (!result) return std::numeric_limits<double>::quiet_NaN();
   double const day = MakeDay(tmp->get(0)->Number(), tmp->get(1)->Number(),
                              tmp->get(2)->Number());
   double const time = MakeTime(tmp->get(3)->Number(), tmp->get(4)->Number(),
                                tmp->get(5)->Number(), tmp->get(6)->Number());
   double date = MakeDate(day, time);
   if (tmp->get(7)->IsNull()) {
-    date = isolate->date_cache()->ToUTC(static_cast<int64_t>(date));
+    if (!std::isnan(date)) {
+      date = isolate->date_cache()->ToUTC(static_cast<int64_t>(date));
+    }
   } else {
     date -= tmp->get(7)->Number() * 1000.0;
   }
   return date;
 }
 
 
 // ES6 section 20.3.4.41.1 ToDateString(tv)
 void ToDateString(double time_val, Vector<char> str, DateCache* date_cache) {
   if (std::isnan(time_val)) {
@@ skipping 1199 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8