Ancient Until the the beginnings of the months of the lunar calendar were based on observation, beginning at dawn on the morning when a waning crescent moon could no longer be seen. The intercalary month was added every two or three years as needed to maintain the
heliacal rising of
Sirius within the
fourth month of the
season of Low Water. This month may have had as many as 30 days. According to the civil calendar, the months fell in order with the rest regardless of the state of the moon. They always consisted of 30 days, each individually named and devoted to a particular patron deity, but the year was always followed by an intercalary month of only five days. Owing to the lack of a leap day, the calendar slowly cycled relative to the solar year and Gregorian date until the
Ptolemaic and
Roman eras. The period of the intercalary month was considered spiritually dangerous and the
pharaoh performed a ritual known as "Pacifying
Sekhmet" ('''') to protect himself and the world from that god's plague. The period seems to have usually been a time of rest, placed between the New Year's Eve celebrations on 30
Wep Renpet and the New Year's celebrations beginning on 1
Thoth. Scribes sometimes omitted the entire period from their records of the year. Torches were carried and
apotropaic charms were drawn on
linen and worn around the neck. The period was known as the "birthdays of the gods" as early as the
Pyramid Texts. By the early
Middle Kingdom, the days were specified and ordered: • The first day was the Birth of
Osiris ('
). It was also originally known as the "Pure Bull in His Field" ('), although that aspect of the intercalary festivities was later moved to the second day as Horus grew in importance. • The second was the Birth of
Horus (''''). • The third was the Birth of
Set (''''). • The fourth was the Birth of
Isis ('
or '). • The last day was the Birth of
Nephthys (''''). It was originally the most important, heralding in the New Year's festival and celebrating a "child in his nest" (''''), but these aspects shifted to the fourth night in the Ptolemaic and Roman period owing to the greater importance of Isis and her longstanding connection with the star
Sirius. Throughout the days, their connections to the solar boat of
Ra, fish, and a "creator of terror" ('''') were also stressed. In all but a handful of texts, however, the days are merely numbered as "Day ~ of the Five Days upon the Year".
Ptolemy III's
Canopus Decree was an attempted calendrical reform in 239BC which would have inserted a sixth day into the intercalary month, but it was abandoned due to the hostility of the priests and people of Egypt. The leap day was finally established by
Augustus in 30, 26, or 25BC. and will continue to do so until AD2100 (Anno Martyrum|1816). In that year, the
Gregorian calendar's lack of a leap day will cause the Coptic month to advance another day relative to it and it will run from 7 September to 11 September. Coptic leap years are not computed as divisors of four in that calendar's
Diocletian era but occur in the year prior to the Gregorian leap year. The Coptic liturgical calendar of the month consists of: ==Ethiopian calendar==