Fix core lib DateTime in the VM.

runtime/lib/date.cc

Index: runtime/lib/date.cc
diff --git a/runtime/lib/date.cc b/runtime/lib/date.cc
index cf92809836bac21d94b09a1861a2534585972dd0..ba9fa95d9117f86178e13ec5bcbba5fedac3152c 100644
--- a/runtime/lib/date.cc
+++ b/runtime/lib/date.cc
@@ -12,13 +12,13 @@
 
 namespace dart {
 
-static int32_t kMaxAllowedSeconds = 2100000000;
+static int64_t kMaxAllowedSeconds = kMaxInt32;
 
 DEFINE_NATIVE_ENTRY(DateTime_timeZoneName, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(
       Integer, dart_seconds, arguments->NativeArgAt(0));
   int64_t seconds = dart_seconds.AsInt64Value();
-  if (seconds < 0 || seconds > kMaxAllowedSeconds) {
+  if (llabs(seconds) > kMaxAllowedSeconds) {
     Exceptions::ThrowArgumentError(dart_seconds);
   }
   const char* name = OS::GetTimeZoneName(seconds);
@@ -30,7 +30,7 @@ DEFINE_NATIVE_ENTRY(DateTime_timeZoneOffsetInSeconds, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(
       Integer, dart_seconds, arguments->NativeArgAt(0));
   int64_t seconds = dart_seconds.AsInt64Value();
-  if (seconds < 0 || seconds > kMaxAllowedSeconds) {
+  if (llabs(seconds) > kMaxAllowedSeconds) {
     Exceptions::ThrowArgumentError(dart_seconds);
   }
   int offset = OS::GetTimeZoneOffsetInSeconds(seconds);