Make a “visual clock”. It is not essential that the time of day be literally readable from it, but your clock should appear different at all times of the day, and it should repeat its appearance every 24 hours. (You can make a 12-hour clock if you prefer). If you do decide to make the time literally readable (e.g. by counting graphic elements, visualizing numeric bit patterns, etc.), you are not permitted to use conventional Roman/Arabic/Chinese etc. numerals.