For iPhone users Calendar App is important software. With the help of this software you can keep a track of all the records of what is happening on any specific date and time. You can also track your important tasks that you have scheduled of the particular day. This can also help you performing useful jobs such as your business meeting, birthday of your family and friends or work schedule, etc. Due to this very reason this app is popular among the iPhone users. Now suppose if your Calendar app has stopped working then in that case you may lose all the important data or task that are saved in it. Or it may also happen that the data may get missing or get deleted by mistake. While upgrading the iOS if it fails then there are chances you may lose the saved data.