Russian holidays for Emacs calendar

This mode adds Russian holidays for GNU/Emacs calendar. Russian Federation is multinational country with own holidays in different regions. The package has info about official state holidays and official regional holidays.

Sources of data

• “Праздники России“
• “Справка о нерабочих праздничных днях, профессиональных праздниках и памятных датах“

There are a lot of differences between documents in internet so please
report about wrong namings and dates.

Restrictions

There is only limited subset of holidays added:

• Only official state holidays counted.
• It based on the modern data for last years so it not applicable to
  previous years or historical holidays.
• It don’t show holidays without fixed calendar dates yet (except Orthodox Easter)
• For regional holidays only dates with official day offs counted (no
  memorial days etc.)

Installation

To use russian-holidays exclusively for the calendar:

 (require 'calendar)
 (require 'russian-holidays)
 (setq calendar-holidays russian-holidays)

To use russian-holidays additionally to other calenders:

 (setq calendar-holidays (append calendar-holidays russian-holidays))

If you’d like to add regional holidays, you can use it like in this
example for Chuvash respublic (regional names use ISO-3166-2 codes):

 (setq calendar-holidays (append calendar-holidays russian-holidays russian-holidays-cu-holidays))

This works for for all regions noted in
https://ru.wikipedia.org/wiki/Праздники_России article.

Calendar variables use regional codes as described in
ISO 31666-2. For
example Tatarstan russian-holidays-ta-holidays, Bashkortostan
russian-holidays-ba-holidays etc.

License

GPLv3 for the code. Calendar data is public domain.

Future

I am interesting for calculating dates of Muslim and Buddhism holidays.