Track movements of the sun throughout the year, anywhere on Earth. Good for learning how the geometry and motions of the sun and Earth dictate the daily and yearly patterns of day and night or finding specific event details.
Can graphically figure:

# time of sunrise and sunset
# true heading of sunrise/sunset
# approximate length of twilight
# time of local noon
# elevation angle of noon sun.

Accuracy of the graphical calculations is about 5 minutes or 5 degrees. Not recommended for the graphically timid.