Final answer:
The ancient Egyptian astronomical calendar was not 365 days long, but rather consisted of 360 days with an additional 5 days added.
Step-by-step explanation:
The statement "The ancient Egyptian astronomical calendar was 365 days long" is false. The ancient Egyptian calendar consisted of 360 days, which was divided into 12 months of 30 days each. However, they noticed that this calendar did not align with the actual solar year, so they added on an extra 5 days at the end of the year to make up for the difference. These additional 5 days were considered to be outside of the normal calendar and were often associated with festivities and celebrations.
Learn more about Ancient Egyptian astronomical calendar