The first idea I have is frog eating flies. Each flies the frog eats represent one hour.
The second idea I have is flower growing/blooming. The growing of each petal of the flower represents one hour and after 12 hours the first flower would disappear and the second flower would appear. Background color changes as the time passes by to represent day time and night time.
The third idea I have is the computer screen shows different numbers in 24 different languages to represent time. Background color changes as the time passes by to represent day time and night time.