I got this timer to turn on and off lights on a reptile aquarium. It works fine. But after a while it got unplugged (I have kids...) and misplaced and we were just turning the lights on and off manually. This went fine until we had to go on a vacation. Then I found that I had misplaced the instructions and could not reprogram it without them. It's not all that intuitive for sure! I looked all over the internet to find a way to get them, but even that was very hard. Finally I found that this model shares instructions with other models under different names. The link can be found here: [...]. One very tricky feature is that various day-program options can "hide" in there. I had a program all figured out for all seven days and the times I wanted, but didn't realize that another conflicting program was in another screen. The upshot of it was that our lizard spent three solid days with the lights on. I recommend that you set this up, using the instructions very carefully, and then test it by letting it run for a few days to make sure you did it right. And keep those instructions in the VAULT. They are a must.