luminary
A Clojure library designed to provide date calculations based on the Bible and the 1st Book of Enoch.
And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.
Usage
Require:
(:require [xyz.thoren.luminary :as l])
Examples:
(l/find-date 5 11)
;; =>
{:hebrew
{:days-in-month 29,
:day-of-week 5,
:month-of-year 5,
:minor-feast-day false,
:day-of-month 11,
:major-feast-day false,
:sabbath false,
:names
{:month-of-year "5th",
:traditional-month-of-year "Av",
:day-of-month "11th",
:day-of-week "5th day of the week"},
:months-in-year 12},
:time
{:year
{:start
#object[java.time.ZonedDateTime 0x2460f316 "2021-04-12T19:06+03:00[Asia/Jerusalem]"],
:end
#object[java.time.ZonedDateTime 0x3c371f7d "2022-04-01T18:57:59+03:00[Asia/Jerusalem]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false},
:month
{:start
#object[java.time.ZonedDateTime 0x6dab6622 "2021-08-08T19:29+03:00[Asia/Jerusalem]"],
:end
#object[java.time.ZonedDateTime 0x58df97d4 "2021-09-07T18:54:59+03:00[Asia/Jerusalem]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false},
:week
{:start
#object[java.time.ZonedDateTime 0x6e7ec90a "2021-08-14T19:23+03:00[Asia/Jerusalem]"],
:end
#object[java.time.ZonedDateTime 0x2ead9123 "2021-08-21T19:15:59+03:00[Asia/Jerusalem]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false},
:day
{:start
#object[java.time.ZonedDateTime 0x2272350f "2021-08-18T19:19+03:00[Asia/Jerusalem]"],
:end
#object[java.time.ZonedDateTime 0xc320d03 "2021-08-19T19:17:59+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
{:days-in-month 30,
:day-of-week 7,
:month-of-year 1,
:minor-feast-day false,
:day-of-month 14,
:major-feast-day
{:name "Passover",
:hebrew-name "Pesach",
:day-of-feast 1,
:days-in-feast 1},
:sabbath true,
:names
{:month-of-year "1st",
:traditional-month-of-year "Nisan",
:day-of-month "14th",
:day-of-week "Sabbath"},
:months-in-year 13},
:time
{:year
{:start
#object[java.time.ZonedDateTime 0xde04680 "2025-03-29T19:32+01:00[Europe/Oslo]"],
:end
#object[java.time.ZonedDateTime 0x6d9bc7a3 "2026-04-18T00:13:59+02:00[Europe/Oslo]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false},
:month
{:start
#object[java.time.ZonedDateTime 0x9725bac "2025-03-29T19:32+01:00[Europe/Oslo]"],
:end
#object[java.time.ZonedDateTime 0x79f65d6d "2025-04-28T21:23:59+02:00[Europe/Oslo]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region true},
:week
{:start
#object[java.time.ZonedDateTime 0x536c7f18 "2025-04-05T21:31+02:00[Europe/Oslo]"],
:end
#object[java.time.ZonedDateTime 0x1cde0d39 "2025-04-12T22:43:59+02:00[Europe/Oslo]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false},
:day
{:start
#object[java.time.ZonedDateTime 0x54ac8d2e "2025-04-11T22:32+02:00[Europe/Oslo]"],
:end
#object[java.time.ZonedDateTime 0x5d8d601e "2025-04-12T22:43:59+02:00[Europe/Oslo]"],
:start-adjusted-for-polar-region false,
:end-adjusted-for-polar-region false}}}
list-of-known-feast-days-in-gregorian-year will list the dates on which holidays start
at the sunset:
(l/list-of-known-feast-days-in-gregorian-year 2021)
;; =>
("2021-01-13 First day of Shevat"
"2021-02-12 First day of Adar"
"2021-02-25 Purim"
"2021-02-26 Shushan Purim"
"2021-03-13 First day of Adar II"
"2021-04-12 First day of Nisan"
"2021-04-25 Passover"
"2021-04-26 First day of the Feast of Unleavened Bread"
"2021-04-27 Second day of the Feast of Unleavened Bread"
"2021-04-28 Third day of the Feast of Unleavened Bread"
"2021-04-29 Fourth day of the Feast of Unleavened Bread"
"2021-04-30 Fifth day of the Feast of Unleavened Bread"
"2021-05-01 Feast of First Fruits"
"2021-05-02 Last day of the Feast of Unleavened Bread"
"2021-05-12 First day of Iyar"
"2021-06-10 First day of Sivan"
"2021-06-19 Feast of Weeks"
"2021-07-10 First day of Tammuz"
"2021-08-08 First day of Av"
"2021-09-07 First day of Elul"
"2021-10-06 Feast of Trumpets"
"2021-10-06 First day of Tishrei"
"2021-10-15 Day of Atonement"
"2021-10-20 First day of the Feast of Tabernacles"
"2021-10-21 Second day of the Feast of Tabernacles"
"2021-10-22 Third day of the Feast of Tabernacles"
"2021-10-23 Fourth day of the Feast of Tabernacles"
"2021-10-24 Fifth day of the Feast of Tabernacles"
"2021-10-25 Sixth day of the Feast of Tabernacles"
"2021-10-26 Last day of the Feast of Tabernacles"
"2021-10-27 The Last Great Day"
"2021-11-05 First day of Marcheshvan"
"2021-12-04 First day of Kislev"
"2021-12-28 First day of Hanukkah"
"2021-12-29 Second day of Hanukkah"
"2021-12-30 Third day of Hanukkah"
"2021-12-31 Fourth day of Hanukkah")
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.
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