Very often in our daily lives, we have daily tasks that are turn based. E.g washing of toilet is to be rotated between you and your spouse. Moping of floor take turns. Wash dishes take turns. Who to take bath first, queue up etc is to be rotated between your kids and many more tasks are turn based. At any one time, you want to know who is the current person supposed to undertake this task. After this time is done, the next person will be the next to do the same task.