Honestly, I wouldn’t know why you would do this, just perhaps for the sake of doing it, but, Kuku Klok gives you an online alarm clock.
You can set the time you need the alarm to go. And, you even have a choice of four different sounds that you would like to listen to.
The best part is that once loaded, the online alarm clock will work even if Internet connection goes down. However, it does mean that you will need to keep your browser window open.
Now, only for a software that does this job