How can I customize the Windows 7 clock to show full date/time?

I'm currently using Windows 7 Ultimate. I've seen that some people have full date/time info in their system tray clock like this:

However, my current system tray clock is shown like this:

I wonder how I could change the clock, but can't find any way to do so without a third party application. Maybe there's a way to hack into registry or something?

I know that I can enlarge the taskbar to get it, but I don't want to lose my screen space that way.

solved: Finally I gave up with the "non 3rd party" idea and use Tclock Light to do it, this small free, portable application do it awesome :D.

Solution 1:

Check out this link. It sounds like what you are looking for.

http://www.howtogeek.com/howto/9235/change-display-under-the-system-tray-clock-in-windows-7/