How to program and build an time lock box?

Dear Arduino Community,
Recently, I have been wanting to build a box that would lock (using servos) for a certain amount of time as determined by the user. For those of you who have read the book “The City of Ember,” this box would be similar to the box containing instructions. This box is a commercial product of what I am trying to build.

I was hoping to have a potentiometer or button to set how much time to lock the box for, and then an lcd screen to display the remaining time. It would be nice to be able to lock the box for many days, or even months. Thanks, and if you have any ideas or suggestions, then please help. Thanks, icecats

icecats: It would be nice to be able to lock the box for many days, or even months.

Have you considered how you're going to power this?

I would probably just keep the box plugged into the wall. Thanks, icecats

If I where you, I'd use a real time clock module (something like http://www.dx.com/p/ds1302-real-time-clock-module-with-battery-cr2032-126453#.U9Z6tfl_shM ) I still have to test mine but the library will probably allow you to count down from seconds up to months. Like you said, a simple LCD would be enough to show the remaining time. buttons are better for what you want to achieve than potmeters. (maybe something like http://www.dx.com/p/jtron-character-lcd-input-output-expansion-board-lcd-keypad-shield-green-black-289132 )?

do you need pseudo code to get you started?

Thanks for all of the tips! I will look into an rtc module. Yes please on the pseudo code. That would be extremely helpful. Thanks, icecats