Ancient Egyptian Calendar

The Egyptian year was divided into three seasons, Inundation, Emergence and Drought (Akhet, Peret and Shomu), each of four months. Each month was 30 days (the symbol for month is the crescent moon).
The year ended with 5 extra days that were celebrated as the birthdays of Osiris, Horus, Seth, Isis and Nephthys.
A day was specified by the day, month and season, say, day 4 of month 2 of Inundation.
The years were numbered by reign, say year 10 of Thutmose III.
A working day typically consisted of two four hour shifts with a lunch break at midday.

The Egyptian New Year is interesting. People in the ancient world gave the New Year special importance, they were less confident than we are today of the regularity of the motions of the stars.
Seafaring cultures often adopted lunar calendars as they related to tides whereas solar calendars were necessary for agriculture.
The Eygyptians were the first Mediterranean people to use a solar calendar, with 12 months of 30 days and five festival days. They had noticed a coincidence, once a year the star Sirius rose straight up from the rising sun and this occurred just before the annual floods of the Nile.

The Egyptian calendar did not take account of the extra quarter of a day in the solar year and thus it was a 'sliding' calendar which corrected itself every 1450 years.

In todays brilliantly lit cities, the power of the night sky is reduced. In past times, when people largely slept under the stars, it possessed a splendour and magic. All over the land people devoted mental activity to the comets and stars.
For the Egyptians the star, Sirius, which was brightest at the beginning of the year, corresponding to the annual flooding of the Nile, had special significance. Meteors when they made earthfall as meteorites were thought to come from the land of the gods (metal of heaven). The Benben stone at Heliopolis was worshiped as such. A birth or death that coincided with a meteorite may have been been given special significance.

The Julian calendar was used from 30 BC.

The mythology of the 5 extra days relates to a curse that Ra put on his granddaughter, Nut (goddess of the sky) on learning she was pregnant.
Ra feared a son would one day replace him so forbade her to give birth on any day of the year.
Nut sought help from Thoth (god of wisdom) who devised a strategy in which he first won a game of senet against Khonsu (god of the moon) with the forfeit of some of his moonlight (so causing the moon to subsequently wax and wane).
With the moonlight Thoth made the extra days and Nut gave birth to Osiris, Horus, Seth, Isis and Nephthys.
Ra's anger was so great that Nut feared for Osiris and so requested Thoth look after him.