How appropriate, as it is night-time now, and the chocolate is calling...
Night eating is a problem for many people, but I guess the first question usually is: is it really that harmful. Well, technically, your body does slow down a bit in preparation for rest, so you will burn a bit less a night that the same snack in the morning. The real problem lies in whether you are eating the bulk of your calories at night, or are spacing them throughout the day and also having a small snack at night.
The former is more harmful than the latter for a couple of reasons. If most of your calories are being consumed at night, then your body really is starving for food all day, and your metabolism is slowing down to accommodate. Then, when you begin to eat, you overcompensate because you are really hungry. You tend to lack the control necessary to stop, and you tend to make less healthy choices. I'm thinking of the tired working person on their way home, who didn't plan dinner, is starving, and ends up at the drive through with 2000 calories worth of McDonald's.
A better approach would be to space those calories throughout the day, and then budget for your nighttime snack, if you like to have something after dinner. Think ahead and plan for your hungry times, making sure you have healthy choices readily available.
Have a great night!