luminary

A Clojure library designed to provide date calculations based on the Bible and the 1st Book of Enoch.

Usage

Require:

(:require [xyz.thoren.luminary :as l])

Examples:

(l/find-date 5 11)
;; => 
{:hebrew
 {:month-of-year 5,
  :months-in-year 12,
  :day-of-month 11,
  :days-in-month 29,
  :day-of-week 5,
  :sabbath false,
  :feast-day false,
  :names
  {:month-of-year "5th",
   :traditional-month-of-year "Av",
   :day-of-month "11th",
   :day-of-week "5th day of the week"}},
 :time
 {:year
  {:start
   #object[java.time.ZonedDateTime 0x7cb6ce48 "2021-04-12T19:06:09+03:00[Asia/Jerusalem]"],
   :end
   #object[java.time.ZonedDateTime 0x1ad646a6 "2022-04-01T18:58:34+03:00[Asia/Jerusalem]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false},
  :month
  {:start
   #object[java.time.ZonedDateTime 0x107e0c2f "2021-08-08T19:29:36+03:00[Asia/Jerusalem]"],
   :end
   #object[java.time.ZonedDateTime 0xdfae2ea "2021-09-07T18:55:23+03:00[Asia/Jerusalem]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false},
  :week
  {:start
   #object[java.time.ZonedDateTime 0x5b64f5e5 "2021-08-14T19:23:43+03:00[Asia/Jerusalem]"],
   :end
   #object[java.time.ZonedDateTime 0x2b8b08e0 "2021-08-21T19:16:08+03:00[Asia/Jerusalem]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false},
  :day
  {:start
   #object[java.time.ZonedDateTime 0x40cb74e6 "2021-08-18T19:19:29+03:00[Asia/Jerusalem]"],
   :end
   #object[java.time.ZonedDateTime 0x7d91e763 "2021-08-19T19:18:22+03:00[Asia/Jerusalem]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false}}}

(l/find-date-in-year 78.2253587 15.4878901 "Europe/Oslo" 2025 1 14)
;; => 
{:hebrew
 {:month-of-year 1,
  :months-in-year 13,
  :day-of-month 14,
  :days-in-month 30,
  :day-of-week 7,
  :sabbath true,
  :feast-day
  {:name "Passover", :hebrew-name "Pesach", :day-of-feast 1, :days-in-feast 1},
  :names
  {:month-of-year "1st",
   :traditional-month-of-year "Nisan",
   :day-of-month "14th",
   :day-of-week "Sabbath"}},
 :time
 {:year
  {:start
   #object[java.time.ZonedDateTime 0x74968291 "2025-03-29T19:32:29+01:00[Europe/Oslo]"],
   :end
   #object[java.time.ZonedDateTime 0x1e60a90e "2026-04-18T00:14:16+02:00[Europe/Oslo]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false},
  :month
  {:start
   #object[java.time.ZonedDateTime 0x530073a2 "2025-03-29T19:32:29+01:00[Europe/Oslo]"],
   :end
   #object[java.time.ZonedDateTime 0x2bafe6d "2025-04-28T21:24:44+02:00[Europe/Oslo]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region true},
  :week
  {:start
   #object[java.time.ZonedDateTime 0x72b2edf3 "2025-04-05T21:31:02+02:00[Europe/Oslo]"],
   :end
   #object[java.time.ZonedDateTime 0x414e156b "2025-04-12T22:44:36+02:00[Europe/Oslo]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false},
  :day
  {:start
   #object[java.time.ZonedDateTime 0x145b19b5 "2025-04-11T22:32:18+02:00[Europe/Oslo]"],
   :end
   #object[java.time.ZonedDateTime 0x2d4b124f "2025-04-12T22:44:36+02:00[Europe/Oslo]"],
   :start-adjusted-for-polar-region false,
   :end-adjusted-for-polar-region false}}}

Background

The Bible instructs believers to keep several Feasts, or Moedim. There are several methods for determining what date it is according to the model described in the Bible. The most common would be the Rabbinic Calendar which is a mathematical calendar based on a lunar month and a solar year, but there are others, such as the Karaite Calendar, which is also has a lunar month and a solar year, but where observation of the new moon is the basis for a 'new month' and the status of the Barley in Israel is the basis for a 'new year'.

This library is based both on The Bible and the 1st Book of Enoch and follows the following conventions:

• A new year will start at the first sunset after the first lunar conjunction following the March Equinox.
• A new month will start at the first sunset following lunar conjunction.
• A new day starts at the sunset.
• The week starts on the evening of what is commonly known as Saturday.
• The Sabbath falls on the last day of the 7 day week.
• For locations outside of Israel, the new year and the new month will fall on the same Gregorian date as they did in Israel. For example, if the next month will start on the eve of March 3rd in Israel, the same will be true for locations where the sunset will come before the lunar conjunction. This is so that everyone will keep the feast days together which would be impossible if one would not base the new year and the new month on the one in Israel.
• For locations where the sun would not rise or set on a particular date, the latitude is adjusted to 65.7/-65.7 for that particular day, making sure that there is always a sunset to start the new day. This is how I imagine keeping the day count if moving to such a location. For days when there is a sunset at the actual coordinates, that sunset will be used.
• The location used to calculate the timing of the new year and the new month is the Temple Mount in Jerusalem.
• The feast of First Fruits falls on the day following the weekly Sabbath during the Feast of Unleavened Bread.
• On leap years Purim falls on Adar I following the Karaite convention.

Contribution

Pull requests are welcome. Especially those related to performance improvements, and of course bug fixes. Please don't open an issue or a pull request to 'fix' the interpretation of Scripture leading to this calendar system. There are many calendar systems out there and I absolutely respect that no one can know with 100% assurance how to calculate these matters until Messiah comes back.

With that being said, I will consider pull requests to support multiple variants, such as sliver calculations, etc.

Acknowledgements

• Sun and Moon calculations are provided by shred's commons-suncalc.
• Equinox calculations are provided by xyz.thoren.equinox.
• All time operations are utilizing clojure.java-time.

License

Copyright © 2021 Johan Thorén

This project is licensed under the GNU Lesser General Public License v3.0.