This is very useful in different situations. For example:
* In the summer time, to help you decide where to park your car when you arrive somewhere in the morning and do not want it to be under the sun when you have to leave in the afternoon.
* When you are visiting a house to rent for your next holidays and want to know at what time of the day there will be sun on the terrace.
* You are preparing an outdoor event and have to decide which is the best time or place depending on whether you prefer sun or shade.
Change the orientation of your phone and you will see in what direction shadows are projected. Slide your finger on the screen to change the time and notice the direction of shadows evolving along the day.
You can also change the date or location to know the evolution of the shadows at any place in the world and on any date of the year.