The program works by letting you define a list of one or more projects that you may be working on. For example, if you're a webpage designer, you may be working on three separate site designs for a government agency, a restaurant, and a car dealership. Each client would be considered a separate project. If you happen to be doing two different types of work for the same client, you can define each as a separate project.
After creating one or more projects, the next step is tracking your time whenever you work on a specific project. Each time you work on a project, click on the Start New Session button to record the amount of time you're spending. When you're done, click the Stop button. OfficeTime now tracks the amount of time you've spent.
If you walk away from your Mac and let it go to sleep, the program even tracks the time your system has been inactive. Now you have a choice of subtracting, ignoring, or keeping this time as part of your billable session.