How to calculate the total time a user spending on an application?

Question

I want to create an application that able to calculate the total time the user (i.e. myself) spent on a particular application, for example Firefox. And this application should

Answer 1

This is not a programming problem. This is a discipline problem. My advises:

1. First of all, don't rely on application to tell you what to do.
2. Secondly, the application can warn you but ultimately you can disable it, turn it off.
3. Thirdly, my suggestion to your real problem i.e. no discipline and poor work ethic is to put up a small banner in front of your monitor with this text "Focus on your work" or "Code it now" or "SO is evil"