Ancient shadow clocks split the daytime into 12 hours.

Once the night was split into 12 parts, it made sense to do the same for the day. Egyptians made shadow clocks, which were early sundials. These clocks used a T-shaped bar placed in the ground. The shadow fell on marks that split the sunny hours into 10 parts. They added two more hours for twilight—one for the morning and one for the evening. This gave them 12 daytime hours.