When you’re developing an application to track time or some work done on a computer, you need to know how long that user was actually in front of the screen, working on a task. If user has left his seat, your application should detect that and pause the timer.
This can be done by comparing user idle time with predefined amount of seconds, for which we are shure that user is left his place, usualy 300 or 600 seconds (5-10 minutes).