In about 280 b.c., an Egyptian historian

In about 280 b.c., an Egyptian historian named Manetho
documented the ancient Egyptian chronology that is still used
today. He divided the historical periods into the Old Kingdom
(which modern historians date from 2700 to 2200 b.c.), the
Middle Kingdom (2050–1800 b.c.), and the New Kingdom
(1570–1090 b.c.). Between the Old and Middle Kingdom came
the First Intermediate period, and between the Middle King-
dom and New Kingdom came the Second Intermediate period.
Manetho identified 30 royal family lines, or dynasties, that ruled
during these times; the New Kingdom, for example, was the
time of the Eighteenth, Nineteenth, and Twentieth dynasties.