Anglican calendar

The purpose of this program is to calculate the holy days of a calendar of an Anglican church for a given year.

The program could be potentially be extended to operate for the calendar of the Book of Common Prayer, and for the calendars of other churches.

Warning: this program is currently in alpha status and may result in incorrect data. Please raise any issues on GitHub.

Also note:

The data used to calculate holy days and dates has been derived from Wikipedia and may be incorrect.
Each national Church of the Anglican Communion has its own calendars including local holy days, and differs from the calendars of other national Churches. Also, dioceses and local churches have discretion to vary calendars, for example upgrading, downgrading, adding or dropping holy days, moving holy days from a weekday to a Sunday and adding the dedication day of a church to the local calendar, so the calendar observed by your local church may differ from the output of these programs.
Disputes over Church calendars seem to have historically caused more heated discussion than any other topic ever. Please do not make this a cause of dissention.
Please raise any issues on GitHub.
Some of the following requires technical knowledge at some level.
There are several calendar projects on GitHub for the Tridentine calendar: here and here. This project is not related to either of these.

How to do

This section describes some of the most common things to do and some guidelines on how to do them.

How to load the holy days of a Church calendar into your calendar program (e.g. Google Calendar) and how to cancel these holy days.
How to generate the holy days for a new year.
How to build the code.
How to modify a calendar or create a new calendar.
How to modify the code.

How to load the holy days of a Church calendar into your calendar

Create a new test calendar in your calendar system for just your Church calendar, and import the holy days into this new calendar. Then, if you want to undo the load and remove all the holy days, you can just delete the test calendar. This is just an alpha version after all.

There are generated calendars in the data/cals directory. Most calendar programs have some way of loading these files into your calendar. You want to load a file with a name like cofe-2019.ical.

Note that there may be a way to subscribe to a calendar over the internet, so if someone can set this up it may be the best solution.

Note: aca = Anglican Church of Australia, cofe = Church of England, ecusa = Episcopal Church of the United States of America, hkskh = Anglican Church of Hong Kong.

How to cancel these holy days out of your calendar

Warning: the following appears not to work with Google Calendar, and has not been tested on anything else. You are probably better off just deleting the entire test calendar. You did load the holy days into a separate test calendar like it says in the previous section, didn't you?. The data/cals directory also contains files with names like cofe-del-2019.ical (with del). These 'should' be able to delete the entries created by the previous calendar.

How to generate the holy days for a new year

Some technical knowledge required.

At the moment, the programs are only distributed in source code form, so you will need to build the conversioin program from the source code (see the next section). In future, there will be pre-built executables for you to download.
Ensure that you have a suitable calendar data file in the format required by this program. These can be found in the data/final directory. If you need a different calendar, see the information below to create your own.
Use the anglican_calendar executable to create a calendar and the associated deletion file. Running this executable with --help will describe the options.

The execution line will be something like ./anglican_calendar -c data/final/cofe.data -i data/cals/cofe-2019.ical -d data/cals/cofe-del-2019.ical -y 2019 -u ang-alpha

Replace cofe and 2019 in the above as required.

The -u parameter is to provide a unique identifier for each holy day to the calendar system (e.g. Google Calendar) so that your calendar app can delete the correct entries using the deletion file (see "How to cancel..." above).

How to build the code

Systems administration knowledge required.

The code is written in the rust programming language, so you will need to install the rust tool chain.
Clone this repository from GitHub.
Build the executables. See the scripts/build.sh script for an idea of how to do this.

How to modify a calendar or create a new calendar

Systems administration knowledge required. Also, this is a mess and unnecessarily difficult to understand.

Your options are:

modify the file in the data/final directory. At the moment, the only documentation for this format is in the source code for the programs. or
use code such as in scripts/make-data.sh to derive a calendar data file from Wikipedia data. Good luck with this; you will need it.
- first replace commas with @ signs where they separate fields in the input data. See files such as data/original/cofe.txt for an example.
- you can use the edit-data executable to modify a calendar data file. This applies some edits (in their own format). It matches edits to holy days using the tag field i.e. the tag nmust be the same on the old holy day entry and the edit modification for the edit to work.

How to modify the code

Application development knowledge required, including the rust programming language.

The code includes documentation which can be displayed using rust tools such as rustdoc. Please see this documentation for additional information about the code internals. Please raise issues and pull requests if you can.

The functionality of the executable

The main executable generates the iCal files.

The functionality of the executable is performed by library crates called from the main program, so that other programs can access the same functions.

Possible future extensions

The following are not in the initial release, but could be added later.

write an HTML file (file path and name) with a report for display and for web applications or write a plain text file (file path and name).
options:
- start year from Advent (default: January 1).
- options for the cases that Common Worship allows (e.g. moving certain holy days to a Sunday, date of celebration of Matthias, etc)
to include in the calendar:
- Sundays e.g. 16th Sunday after Trinity
- Fridays and other fasts (eves)
- ember days
- seasons and martyrs (in colour)

Points to note

the same holy day may have slightly different names in different province and calendars. Holy Days can have 'tags' which are supposed to be consistent across calendars to enable the merger of calendars and overriding of holy day details as required.
some minor holy days may be 'bumped' (transferred) by major holy days. See the rules.
- note: only fixed holy days are moved, except that Patronal and Dedication replace Sunday.
- further discussion of bumping below.
some holy days may not occur in some years e.g. whether there is, or is not, a 23rd Sunday after Trinity will depend on the date of Easter in the year and the date of Advent in the following year.

Bumping (transfer) of holy days

The program ensures that dates are bumped correctly [hopefully].

It processes non-transferable holy days first; then checks all other holy days as to whether each should be transferred.
Holy Days in the calendar are marked by a transfer type. The holy days with the more complex rules have their own transfer type. Note: a specific calendar may possibly not use the transfer type that is normally used for a specific holy day; and this may mean that a new calendar with an different bump rule may only be handled after the code has been enhanced to cover the new rule.

Derivation of the data

The calendar files that are input into the program are generated by the process_data program, which inputs calendar data extracted frm Wikipedia, as listed in the list of Anglican Church calendars. The process_data program only reads the wiki markup for the actual list of holy days, so that needs to be extracted and placed in a file.

kmoe/anglican_calendar