What method did the ancient Egyptians invent to measure time?

The ancient Egyptians first made calendars. According to the 12 constellation in the sky, a year was divided into 12 months, with 30 days in each month and 5 days as a solar year. The ancient Egyptians also invented a timing system, which divided day and night into equal time intervals of 12, and divided the dial scale of the sundial into two hours of 12. This method was later inherited by the Greeks and Romans.