One of the greatest gifts to the world from organised religions is the Calendar. Today we don’t think so much of the calendar as a religious instrument, but that is where it originated.
At some level religions are based on augury and prophesy. Augury is the reading of signs. Prophesy is the foretelling of events in the future. If a religion could correctly interpret signs, and use these to foretell events, it was able to give an advantage to its followers.
In the early days of religion the priests struggled a lot with the concepts of augury in particular. Were two eagles flying from the west a good or a bad thing? Was it good at sunset and bad at sunrise? The struggle to get a handle on Augury was complicated by the natural inclination of the human brain to impose patterns on random occurrences.
As a result you get silly reactions to natural disasters, such as the sacrifice of a virgin to appease the deity who is causing the earthquakes.
As time went by some religions began to use writing systems to document their augury. They tracked the movements of planets and stars. They observed the patterns in the weather. They tracked the movements of animals. They recorded the health of the liver of sacrificed goats.
Over long periods of time certain clear and strong auguries began to emerge. Religions came to understand the timing of seasons. This allowed them to plant crops at the right time. They measured tidal flows and ocean currents. They documented the solar and lunar years and the longer periods of time measured by the alignments of stars and planets and the precession of the universe.
Weather forecasting auguries also became better. They came to understand the patterns of regular seasonal rains and floods, such as the Indian Monsoons and the Egyptian Nile inundation. These events have a significant influence on agriculture and hunting. The Egyptians developed a tool, the Nileometer, to assess the annual flood. The data from the measurements was used to calculate harvest yields and associated taxes. They also developed sophisticated mathematical systems to underpin their calculations, such as quadratic equations. One theory is that the command of mathematics then enabled the Egyptians to develop their monumental architecture.
Earlier calendars broke the solar year down by lunar cycles. A lunar cycle is 28 days. Divided in 4 it gives us the seven day week. But the lunar and solar years do not align perfectly. This became a major challenge for religions. Seasons kept shifting out of alignment as time went by.
The Jewish religious calendar is a good example of this system. It evolved from an earlier Babylonian model and was improved upon over time.
The poster boy of the calendar world is Julius Caesar. As Pontifex Maximus (High priest) of Rome he was head of the College of Pontiffs and had authority over the other three religious Colleges; the Augurs, the Quindecimviri (who carried out rites) and the Epulones (who organised feasts and festivals).
During the Civil War the religious observances in Rome were allowed to slip. The annual calculation of the “intercalends” was not carried out. This was an additional month inserted periodically to bring the Lunar cycle into alignment with the Solar year.
Better calendars were already in use in Persia (Zoroastrian) and Egypt, and it is likely that Caesar experienced the Egyptian calendar personally and was able to assess it. He introduced his new calendar in the year 46BC and had to make the year 446 days long to align correctly.
The Julian calendar was 365.25 days long, and lost only 3 days every 400 years. This was a vast improvement over all existing calendars of the day. It quickly became the established calendar of the Roman Empire and persists in use today in Ethiopia and amongst the Berber of North Africa.
With such an accurate calendar available one would have to question why, on this day in the year 622 CE the Muslims accepted a calendar of 354 days per year. When Allah was talking to the Prophet (Peace be upon him) could he not have suggested that Islam adopt the more accurate model that was available at the time?
Ultimately it fell to Pope Gregory in 1582 to make a minor adjustment to the Julian calendar. The primary motivation was to align the date of Easter correctly to Catholic dogma. In the process the year was corrected to 365.2425 days. Instead of losing 1 day in 128 years (Julian) the Gregorian calendar loses only 1 day in 3,226 years.
In order to remember how many days are in each month children are taught a poem or rhyme as a mnemonic device. This is the one I learned. Is yours any different?
The Calendar Poem
Thirty days has September,
April, June and November,
all the rest have thirty one,
except February alone,
which has four and twenty four
and each leap year gives it one day more.