time & date in the dock?

I was looking through desktop screenshots on spymac the other day and noticed some guy has his time and date placed into the dock. for example, if you go to system preferences and click date and time then have the option to have it in the menu bar or in the window.....well his icon in the dock looked exactly like that time and date that was in the window option when it goes on ur desktop. It looks really cool and i'd like to know how to do it but i can't figure it out and i've looked for similar programs but nothing is really that good. Thanks in advance.