Set hardware clock on linux not working

when i try to set the computer hardware clock like here descripted:

How Do You Programmatically Set the Hardware Clock on Linux?

its开发者_开发技巧 not working (the time is not updated to the new time).

fd = open("/dev/rtc", O_RDONLY); //<- return 3

ioctl(fd, RTC_SET_TIME, &rt); //<- return 0

When I add

system("/sbin/hwclock --systohc");

I get:

Cannot access the Hardware Clock via any known method

Executing hwclock --systohc from the terminal working.

It's a Ubuntu 10.10 mashine in VirtualBox.

I using Code::Blocks 10.05 with GCC 4.4.5

Here is my full source code:

http://pastebin.com/sgBBv1XA

And yes, I execute the programm as root.

I doubt, if it is possible to set HD clock in a machine running in virtual environemnt.