About a hundred years ago a hoard of wonderfully preserved, 2,500-year-old papyri were uncovered on Egypt’s Elephantine Island, in the Nile River in southern Egypt. These bills of divorce, commercial contracts and other legal documents were written in Aramaic, the language of Elephantine’s Jewish and Persian settlers (Egypt was conquered in 527–525 B.C. by the Persians, who employed Jews from Palestine as mercenaries to guard Egypt’s southern border).

These papyri often record events using both the Babylonian lunar calendar and the Egyptian non-lunar calendar. They thus provide a record of dates reaching back as far as the fifth century B.C. In the following text, for example, the date of the manumission of a female slave and her daughter is recorded in both calendars—which turns out to be June 12, 427 B.C., in the modern calendar: