The ancient Egyptian year consisted of 365 days; but after the introduction of the Julian calendar, the astronomers of Alexandria adopted an intercalary year, and added six additional days instead of five to the end of the last month of every fourth year.
Had the internal contacts alone been used, which many astronomers would have considered the proper course, the result would have been 8.776" In 1877 Sir David Gill organized an expedition to the island of Ascension to observe the parallax of Mars with the heliometer.
Observatories were attached to the temples, and reports were regularly sent by the astronomers to the king.
Astronomers denote the year which preceded the first of our era by o, and the year previous to that by 1 B.C.; but chronologers, in conformity with common notions, call the year preceding the era 1 B.C., the previous year 2 B.C., and so on.
It is necessary to remember that by astronomers and by some historians the era is assigned to the preceding day, July 15.