turn on write to SD turn off


I'm trying to put together a project to keep track of time spent on separate jobs at work. I would like to push one of four buttons, the arduino turn on write the button number and time/day to an SD card then turn off so that is not running all the time. The only hangup I have is some sort of circuit to turn the arduino on temporarily, I would like it to stay on till the arduino triggers the power circuit to turn off, to confirm it finished writing to the SD card.

Electrical engineering is not my strong suit so I apologize if I asked any stupid questions. I have tried googleing to get help but its hard to google something like this.

Thank you for any possible help Clay

Think I may have found what Im looking for http://www.pololu.com/catalog/product/750

Or at least it gives me info for what I should be googleing for

I would use a 4072 4-input-or gate to generate the interrupt, then read the status of those 4 inputs (which are connected individually to 4 inputs of the processor). The processor should be in sleep mode most of the time and awaken when any of the buttons is pressed.