This little lib is used to keep track of time using the low resolution timer provided by the OS (in Windows “GetTickCount”). The goal of this type of library is to encapsulate timing actions. It was originally designed for game development in mind but needless to say you can use it and adapt it to your own needs.
Basically you define a time interval as you create the “timelapse” instance. Every time you call the update function a simple check determines whether the time was reached or not. This is trivial, but encapsulating it makes sense. Specially if you plan to create an animation system in the future!