I created the idea of making and using my Dream Clock out of mainly from the challenge of wanting to do great things over the course of a single night’s LD rather than having to make multiple revisits to that same dreamscape. Of course this was before I came to realize how I start to miss things when I’m gone for too long, which is why I only now use my Dream Clock when I really feel like taking a dream vacation 
As for how it works, it works by keeping track of two different sets of time. How much real time I wish to spend dreaming, and how much dream time I wish to spend within that frame of real time.
For example–I wish to spend a week in a dreamscape, say the dreamscape of Tech, to jam to music for seven days straight. I’m going to go to bed and I wish to sleep for just a normal seven hours.
I key into my DreamClock:
[168 Hours Dream Time]
[7 Hours Real Time]
Upon doing that, I then press the simple green Start Button and off I go. Of course, this doesn’t necessarily have to be done on some dream object–my Dream Clock can be used through the simple use of a Heads-Up Display.
Heck you can even put the Dream Clock on a singing fish, and it’ll work all the same.