The first thing to know about Samhain is that it’s based on a different calendar. The bulk of the world operates on the Gregorian calendar. This is the one we’re all familiar with; the first day of the year is January 1, the last day is December 31. The Gregorian calendar was established in 1582 by Pope Gregory XIII, as a reform of the Julian calendar. The Julian calendar was established in AUC 709, or 45 BCE, by Julius Caesar, as a reform of the traditional Roman calendar, which only had ten months. (AUC or AVC refers to the number of years since the founding of the Roman Republic. Obviously no one in 45 BCE knew that they were living “before the common era,” or “before Christ.”)
I cannot possibly give you a rundown of how the calendars came to be the way they are; I just spent half an hour down a calendar nerd rabbit hole and the conclusion is: it’s so very complicated. There’s a lot of math and astronomy and more than a dash of astrology. Rulers of many nations would just rename a month after whomever they pleased, not to mention that before the western world agreed in general to the Gregorian calendar, different people and countries used different methods for calculating the turning of the year. And when I say “before,” please note that the bulk of Eastern Europe adopted the Gregorian calendar in the early 20th century, and Saudi Arabia adopted it in 2016. If I’ve piqued your curiosity, I recommend David Ewing Duncan’s Calendar: Humanity’s Epic Struggle to Determine a True and Accurate Year.
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What is Samhain?