File: cal-bahai.el.html

This collection of functions implements the features of calendar.el and diary-lib.el that deal with the Bahá’í calendar.

The Bahá’í (https://www.bahai.org) calendar system is based on a solar cycle of 19 months with 19 days each. The remaining
"intercalary" days are called the Ayyám-i-Há (days of Há), and are
placed between the 18th and 19th months. They are meant as a time of festivals preceding the 19th month, which is the month of fasting. (Há has the numerical value of 5 in the arabic abjad, or letter-to-number, reckoning).

Each month is named after an attribute of God, as are the 19 days
-- which have the same names as the months. There is also a name
for each year in every 19 year cycle. These cycles are called Váhids. A cycle of 19 Váhids (361 years) is called a Kullu-Shay, which means "all things".

The calendar was named the "Badí‘ calendar" by its author, the Báb. It uses a week of seven days, corresponding to the Gregorian week, each of which has its own name, again patterned after the attributes of God.

CALENDAR REFORM (2014/172 BE): Prior to 172 BE (before Naw-Rúz 2015 CE), Naw-Rúz was fixed at March 21 and leap years followed the Gregorian pattern.

From 172 BE onwards, the Universal House of Justice implemented astronomical observations:
- Naw-Rúz is determined by the vernal equinox as observed from Tehran
- Naw-Rúz can fall on March 19, 20, 21, or 22
- Ayyám-i-Há has 4 or 5 days depending on the gap between successive
  Naw-Rúz dates (ensuring month 19 always ends the day before Naw-Rúz)
- Days run from sunset to sunset; if the equinox occurs before sunset
  in Tehran, that day is Naw-Rúz; otherwise the next day is Naw-Rúz

The implementation uses official tables from the Nautical Almanac Office for years 172-221 BE (2015-2064 CE), and astronomical calculations for years beyond this range.

Note: The days of Ayyám-i-Há are encoded as zero and negative offsets from the first day of the final month. So, (19 -3 157) is the first day of Ayyám-i-Há, in the year 157 BE.

Defined variables (9)

Defined functions (25)

Defined faces (0)