From 50c722196fc2e93f2d274b8ce343039ed794c903 Mon Sep 17 00:00:00 2001 From: Quantum Date: Wed, 23 Jul 2025 21:08:19 -0400 Subject: [PATCH] mcal: explain what the Long Count is --- mcal/public/index.html | 77 ++++++++---------------------------------- 1 file changed, 14 insertions(+), 63 deletions(-) diff --git a/mcal/public/index.html b/mcal/public/index.html index b4db4de..bbc2b02 100644 --- a/mcal/public/index.html +++ b/mcal/public/index.html @@ -70,11 +70,7 @@ the Wayebʼ;
  • The Long - Count, a modified base-20 system used to represent the number of days since the - mythical date of creation, which is August 11, 3114 BCE in the proleptic Gregorian calendar or - September 6, 3114 BCE in the proleptic Julian calendar. It is typically represented as five numbers - separated by dots, with each number counting from 0 up to 19, except for the second last number, - which counts from 0 to 17. + Count, represents the absolute number of days since the Mayan date of creation.

    • Since the Haabʼ is the closest equivalent to months in the Mayan system, this calendar @@ -123,64 +119,19 @@

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    What's so special about this version?

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    Most versions of the calendar floating around doesn't use the original definition above.

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    Most versions uses the so-called Romme method for leap years, using the same leap year rules as - the Gregorian calendar, i.e. every year divisible by four, except century years not divisible by 400. - This method might make sense, except years 3, 7, and 11 were leap years under the original rules and - were observed as such in real life, but the Romme method instead makes years 4, 8, 12 leap - years instead.

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    This version uses the original rules. The JPL's - DE440 and DE441 ephemerides were used to calculate the exact timings of the autumnal equinoxes - between the Gregorian years 13201 BCE and 17191 CE (corresponding to the French Republican years -14991 - to 15399). The times were then converted to UT1+00:09:21, the exact local time at the Paris Observatory. - UT1 was chosen to keep track of the Earth's rotation without having to worry about the issues posed by - leap seconds in UTC. Note that due to the uncertainty over - ΔT — the difference between UT1 and - Terrestrial Time (TT) used in the ephemerides — it is theoretically possible for there to be - inaccuracies when the equinox occurs very close to midnight.

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    For more details about how I calculated this calendar, please see - my blog - post on the topic. This is the fourth part of a series on time-keeping, and you are highly - encouraged to read the - first - three - parts - for a more complete understanding.

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    What are those names above the Gregorian date?

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    Those are the names of the days in the - rural version of the - calendar. This was intended to replace the Catholic Church's calendar of saints, as the French - Revolution wanted to reduce the influence of the church. Every day of the year has a unique name - associated with the rural economy and these names are supposed to correspond with the season.

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    Every quintidi is named after an animal, every décadi is named after an agricultural - tool, and the remaining days are named after various plants or produce. The only exception is the winter - month of Nivôse, which has the remaining days named after minerals.

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    What are those numbers below the Gregorian date?

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    The five (or more) numbers separated by dots is the corresponding - Mesoamerican Long Count - calendar date. This is commonly known as the “Mayan calendar.” This calendar is not - available for dates before August 11, 3114 BCE (25 Thermidor -4905).

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    What is decimal time?

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    Decimal time is a time system used during the French Revolution that divided the day into 10 - hours, each with 100 minutes, which contained 100 seconds each.

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    The result is 100,000 seconds in one day, compared to the 86,400 seconds with the normal 24-hour - system. This makes it very easy to denote time as a decimal fraction of a day. For example, decimal time - 5:67:72 (around 13:37:31) on January 1, 2000 can be represented as 2000-01-01.56772.

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    Also note that each decimal hour is 2.4 normal hours, each decimal minute is 1.44 normal minutes, and - each decimal second is 0.864 normal seconds.

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    How does the Long Count work?

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    The Long Count calendar is a count of days since the Mayan date of creation, which is August + 11, 3114 BCE in the proleptic Gregorian calendar or September 6, 3114 BCE in the proleptic Julian + calendar.

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    It uses a modified base-20 system to represent this number, with each “digit” counting from 0 + up to 19, except for the second last “digit,” which counts from 0 to 17. Typically, five + numbers are shown, separated by dots, but in theory, more numbers could be used for dates in the distant + future.

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    For example, the date 13.0.0.0.0 represents exactly 13×20×20×18×20 = + 1 872 000 days since the date of creation, which is December 21, 2012 CE.

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    Each “digit,” of the Long Count have a name, from the rightmost: kʼin, winal, tun, kʼatun, + bʼakʼtun, piktun, kalabtun, kʼinchiltun, alautun, hablatun. Terms from bʼakʼtun and beyond were invented + by modern scholars and were not used by the classical Maya.