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The problem with ancient (and modern) calendars

Continuing on the calendars theme, let’s devote some time to the biggest problem with calendars.

The problem with calendars is that they try to explain two things which are not identical – the phases of the moon, and the seasons of the year.

The moon circles around the earth in a 28-day orbit, and when observed from the earth, the sun hits the moon in particular ways during that 28-day cycle – for example, the full moon, when the entire moon is illuminated by the sun, and the new moon, when the moon cannot be seen from the earth.

But at the same time that the moon circles around the earth, the earth itself is circling around the sun. This dictates certain things, such as the longest day of the year and the shortest day of the year.

And the two rotations do not agree. Consider the Islamic calendar, which is a lunar calendar. When this is contrasted with the Gregorian calendar, which is (primarily) a solar calendar, you find that the Islamic calendar is much shorter. In Islamic countries that use both calendars, this means that specific Islamic holy days occur earlier and earlier on the solar calendar. Presently, the month of Ramadan occurs in the summer in the Northern Hemisphere. But as time passes, the month will be observed in the spring, then in the winter, then in the autumn, and eventually in the summer again.

The earlier calendars were lunar calendars, presumably because the phases of the moon are much easier to observe. But this caused problems for the ancient people of Egypt:

The earliest Egyptian calendar was based on the moon’s cycles, but the lunar calendar failed to predict a critical event in their lives: the annual flooding of the Nile river.

And if you’re an Egyptian and you don’t know when the Nile is going to flood, you will have serious problems. The solution?

The Egyptians were probably the first to adopt a mainly solar calendar….[T]hey devised a 365-day calendar that seems to have begun in 4236 B.C.E., the earliest recorded year in history.

But what of the calendar that we use today? It is derived from the Julian calendar, created by Julius Caesar to solve a problem with politicians.

Before the Julian calendar was introduced, priests in the Roman Empire exploited the calendar for political ends, inserting days and even months into the calendar to keep the politicians they favored in office. Tired of the chaos that this undependable system eventually gave rise to, Julius Caesar finally set out to put the long-abused calendar back on track.

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