36. Egypt, an absolute date

A Babylonian-Egyptian double date found on a papyrus is the earliest absolute Egyptian date. It corresponds to 2 November 473 BC. From that time on, the correlation between the Babylonian and Egyptian calendars appears satisfactory.

Ptolemy was still using the Egyptian calendar 600 years later. Though he lived near Alexandria, astronomical data from pre-Hellenistic Egypt is conspicuously absent from his work. Worthwhile ancient Egyptian observations were unavailable in his day and they remain scarce today.