Have a loved one who is going to be away for a while? Want to keep track of when they left and when they will return? This is similar to the spreadsheet that is floating around the web for creating a "donut" depicting how much time has passed since an event started, and how much time remains until it ends. Many people with loved ones in the service and stationed overseas use it to know when they will come home. You could also use it to track when a rotating schedule starts and ends. You can make multiple "donuts", and save them for recall later.