Once I got the time and date set, it worked very well. I gave it 4 stars because I almost gave up before I got the time and date set. The instructions are terrible. It says to press the on/off button and the year will show, but each time you push it, it starts to inflate. You have to push and Hold the button until it finally flashes the date. Then you can follow the rest of the directions. Also, it has a place for an AC charger, but it doesn't come with one. It takes 4 AA batteries. But, again. it seems to work very well.