Activate Windows 8 error with the clock time

Hi there,
I want to activate Windows 8 and I have this weird error when I want to do this. My Date and Time are correct and I still have this error about. Can anyone help me please to activate my Windows ? Why I have this error ?
Thanks !

Windows can’t activate right now. Try activating again later. If that doesn’t work contact support.
Error code: 0xC004B011
Error description: The activation server determined that your computer clock time is not correct. You must correct your clock before you can activate.
