How can I validat the date

static void validatedate(Args _args)
{
int num1,num2;
str datevar;
date date1;
datevar = "31.4.2007";

date1 = str2date(datevar,123);
print date1;
numbr1 = str2int(substr(datevar,0,2));
numbr2 = dayofmth(date1);
if (num1 > num2)
print "invalid date";
}