_variant_t does not compare VT_DATE via == operator

VC80 does not compare VT_DATE via == operator in a good manner.
I expect the following to work, but it does not either.
double time_dif = abs(TimeStamp.date- xml_time.date);
bool time_ok = false;
if(time_dif <= (std::numeric_limits::min)())
time_ok = true;
at last I compare time_dif with 0.00000000001