Given a time and place, you can calculate the sunrise and sunset of that day, the moon and the moon phase.
Despite being in modern society, many human activities are closely related to the operation of the sun and moon, and it is also important to know when it is completely dark and when it is dawn.
The sun is highest at noon, but during the year, the northern hemisphere has the highest summer seopth at noon, and those who live by the sea will find that the tides are greatest when the new or full moon is in full.
This is a very practical APP that helps us understand the laws of day and month.