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Ruby gem for calendar computations according to the Roman Catholic liturgical calendar as instituted by MP Mysterii Paschalis of Paul VI. (AAS 61 (1969), pp. 222-226). The rules are defined in General Norms for the Liturgical Year and the Calendar (English translation).

calendarium-romanum aspires to become the most complete FOSS implementation of this calendar system (see list of implementations available).


  • [x] liturgical season
  • [x] Sundays, temporale feasts
  • [x] sanctorale calendars: data format, example data files, their loading
  • [x] resolution of precedence of concurrent celebrations
  • [x] octave days
  • [x] commemorations in the privileged seasons where memorials are suppressed
  • [x] transfer of suppressed solemnities
  • [x] optional transfer of important solemnities to a Sunday
  • [x] additional temporale feasts (Christ the Eternal Priest and similar)


includes an important bit of code from the easter gem by James Robertson


freely choose between GNU/LGPL 3 and MIT

Project status, Backward compatibility

The gem's public interface still evolves and each minor release contains several breaking changes. There is no backward compatibility between minor versions. This will continue until release of v1.0.0.

When using the gem in your projects, it is recommended to lock the dependency to a particular minor version.

In your app's Gemfile

gem 'calendarium-romanum', '~>0.5.0'

or in gemspec of your gem

spec.add_dependency 'calendarium-romanum', '~>0.5.0'


For more self-explaining, commented and copy-pastable examples see the examples directory.

All the examples below expect that you first required the gem:

require 'calendarium-romanum'

1. Typical usage

The easiest way to obtain calendar entry of a liturgical day:

I18n.locale = :en # set locale

# build calendar
pcal =
  sanctorale: CR::Data::GENERAL_ROMAN_ENGLISH.load

# query
day =, 1, 1))

For explanation see the detailed steps below.

2. What liturgical day is it today?

PerpetualCalendar used in the example above is very a high-level API. In order to understand what's happening under the hood, we will now take a lower-level approach and work on the level of a simple Calendar. Each Calendar instance describes a particular liturgical year. We may not know which liturgical year our day of interest belongs to, but fortunately there is "alternative constructor" Calendar.for_day() to rescue:

date =, 8, 19)
calendar = CalendariumRomanum::Calendar.for_day(date)
day =

day.season # => #<CalendariumRomanum::Season:0x00000001d4cfa0 @symbol=:ordinary, @colour=#<CalendariumRomanum::Colour:0x00000001d4d928 @symbol=:green, @i18n_key="">, @i18n_key="temporale.season.ordinary">
day.season.equal? CalendariumRomanum::Seasons::ORDINARY # => true

# => [#<CalendariumRomanum::Celebration:0x00000001c69cc8 @title="Friday, 20th week in Ordinary Time", @rank=#<CalendariumRomanum::Rank:0x00000001d4c708 @priority=3.13, @desc="rank.3_13", @short_desc="rank.short.ferial">, @colour=#<CalendariumRomanum::Colour:0x00000001d4d928 @symbol=:green, @i18n_key="">, @symbol=nil>]
c = day.celebrations.first
c.title # => "Friday, 20th week in Ordinary Time"
c.rank # => #<CalendariumRomanum::Rank:0x00000001d4c708 @priority=3.13, @desc="rank.3_13", @short_desc="rank.short.ferial">
c.rank.equal? CalendariumRomanum::Ranks::FERIAL # => true
c.rank < CalendariumRomanum::Ranks::MEMORIAL_PROPER # => true
# => #<CalendariumRomanum::Colour:0x00000001d4d928 @symbol=:green, @i18n_key="">

Calendar#day returns a single Day, describing a liturgical day. Each day belongs to some #season; every day, we can choose from one or more #celebrations to celebrate. (The only case with multiple choices is combination of a ferial with one or more optional memorials; higher-ranking celebrations are always exclusive.)

Each Celebration is described by a #title, #rank and #colour.

3. But does it take feasts of saints in account?

Actually, no. Not yet. We need to load some calendar data first:

CR = CalendariumRomanum
loader =
sanctorale = loader.load_from_file 'data/universal-en.txt' # insert path to your data file
date =, 8, 19)
calendar = CR::Calendar.for_day(date, sanctorale)
day =
day.celebrations # => [#<CalendariumRomanum::Celebration:0x000000027d9590 @title="Friday, 20th week in Ordinary Time", @rank=#<CalendariumRomanum::Rank:0x000000029e1108 @priority=3.13, ... >, @colour=#<CalendariumRomanum::Colour:0x000000029e1f68 @symbol=:green>>, #<CalendariumRomanum::Celebration:0x000000029c96c0 @title="Saint John Eudes, priest", @rank=#<CalendariumRomanum::Rank:0x000000029e1180 @priority=3.12, ... >, @colour=#<CalendariumRomanum::Colour:0x000000029e1f18 @symbol=:white>>]

(Note how we saved some typing by defining new constant CR referencing the CalendariumRomanum module.)

Unless a sanctorale is loaded, Calendar only counts with temporale feasts, Sundays and ferials.

4. Isn't there an easier way to get sanctorale data?

Yes! There are a few data files bundled in the gem. You can explore them by iterating over CalendariumRomanum::Data.all. The more interesting ones are additionally identified by their proper constants, e.g. CalendariumRomanum::Data::GENERAL_ROMAN_ENGLISH. Bundled data files can be loaded by a handy shortcut method #load:

CR = CalendariumRomanum
sanctorale = CR::Data::GENERAL_ROMAN_ENGLISH.load # easy loading
date =, 8, 19)
calendar = CR::Calendar.for_day(date, sanctorale)
day =

5. I don't want to care about (liturgical) years

Each Calendar instance is bound to a particular liturgical year. Calling Calendar#day with a date out of the year's range results in a RangeError:

CR = CalendariumRomanum
calendar =
  day =, 1, 1))
rescue RangeError
  STDERR.puts 'ouch' # will happen

The example demonstrates the well known fact, that the civil and liturgical year don't match: 1st January 2000 does not belong to the liturgical year 2000-2001 (which will begin on the first Sunday of Advent, i.e. on 3rd December 2000), but to the year 1999-2000. For the sake of simplicity, calendarium-romanum denotes liturgical years by the starting year only, so you create a Calendar for liturgical year 1999-2000 by calling

We have already seen Calendar.for_day(), which takes care for finding the liturgical year a particular date belongs to and creating a Calendar for this year. But maybe you want to query a calendar without caring about liturgical years altogether, possibly picking days across multiple years. The best tool for such use cases is PerpetualCalendar.

CR = CalendariumRomanum
pcal =

# get days
d1 =, 1, 1))
d2 =, 1, 1))
d3 =, 1, 1))

# get Calendar instances if you need them
calendar = pcal.calendar_for_year(1987)

Just like Calendar with the default settings (no sanctorale data etc.) is usually of little use, so is a PerpetualCalendar creating such Calendars. Of course it is possible to specify configuration which is then applied on the Calendars being created:

CR = CalendariumRomanum

pcal =
  # Sanctorale instance
  sanctorale: CR::Data::GENERAL_ROMAN_ENGLISH.load,
  # options that will be passed to
  temporale_options: {
    transfer_to_sunday: [:epiphany],
    extensions: [CR::Temporale::Extensions::ChristEternalPriest]
d =, 1, 1))

# It is also possible to supply Temporale factory instead of options:
pcal =
  # Proc returning a Temporale instance for the specified year
  temporale_factory: lambda do |year|, transfer_to_sunday: [:ascension])
), 1, 1))

Memory management note: By default, PerpetualCalendar caches each created Calendar instance perpetually. This is OK in most cases, but it can lead to memory exhaustion if you traverse an excessive amount of liturgical years. In such cases you can supply your own cache (a Hash or anything with hash-like interface) and implement some kind of cache size limiting.

CR = CalendariumRomanum
my_cache = {}
pcal = my_cache)

Sanctorale Data

Use prepared data or create your own

The gem expects data files following a custom format - see README in the data directory for it's description. The same directory contains a bunch of example data files. (All of them are also bundled in the gem and accessible via CalendariumRomanum::Data, as described above.)

universal-en.txt and universal-la.txt are data of the General Roman Calendar in English and Latin.

The czech-*.txt files, when layered properly, can be used to assemble proper calendar of any diocese in the Czech Republic.

Implement custom loading strategy

In case you already have sanctorale data in another format, it might be better suited for you to implement your own loading routine instead of migrating them to our custom format. SanctoraleLoader is the class to look into for inspiration.

The important bit is that for each celebration you build a Celebration instance and push it in a Sanctorale instance by a call to Sanctorale#add, which receives a month, a day (as integers) and a Celebration:

include CalendariumRomanum
sanctorale =
celebration ='Saint John Eudes, priest', Ranks::MEMORIAL_OPTIONAL, Colours::WHITE)
sanctorale.add 8, 19, celebration

date =, 8, 19)
calendar = Calendar.for_day(date, sanctorale)

day =
day.celebrations # => [#<CalendariumRomanum::Celebration:0x000000010deea8 @title="", @rank=#<struct CalendariumRomanum::Rank priority=3.13, desc="Unprivileged ferials", short_desc="ferial">, @colour=:green>, #<CalendariumRomanum::Celebration:0x000000010fec08 @title="Saint John Eudes, priest", @rank=#<struct CalendariumRomanum::Rank priority=3.12, desc="Optional memorials", short_desc="optional memorial">, @colour=:white>]

(Note that this time some typing was saved by including the CalendariumRomanum module into the current namespace.)

I18n, or, how to fix names of temporale feasts

One drawback of the current implementation is that names of temporale feasts are totally independent of sanctorale feast names. They are hardcoded in the gem, as i18n translation strings.

When you load sanctorale data in your favourite language, the Calendar will by default still produce temporale feasts with names in English. This can be fixed by changing locale to match your sanctorale data.

I18n.locale = :la # or :en, :fr, :it, :cs

The gem ships with English, Latin, Italian, French and Czech translation. Contributed translations to other languages are most welcome.

Transfer of solemnities to a Sunday

As specified in General Norms for the Liturgical Year and the Calendar 7, the solemnities of Epiphany, Ascension and Corpus Christi can be transferred to a Sunday. Temporale by default preserves the regular dates of these solemnities, but it has an option to enable the transfer:

CR = CalendariumRomanum

# transfer all three to Sunday
temporale =, transfer_to_sunday: [:epiphany, :ascension, :corpus_christi])

Usually you don't want to work with Temporale alone, but with a Calendar. In order to create a Calendar with non-default Temporale settings, it is necessary to provide a Temporale as third argument to the constructor.

CR = CalendariumRomanum

year = 2000
sanctorale = CR::Data::GENERAL_ROMAN_ENGLISH.load
temporale =, transfer_to_sunday: [:epiphany])

calendar =, sanctorale, temporale)

Custom movable feasts

Some local calendars may include proper movable feasts. In Czech Republic this has recently been the case with the newly introduced feast of Christ the Priest (celebrated on Thursday after Pentecost). Support for this feast, celebrated in several other dioceses and religious institutes, is included in the gem as Temporale extension.

In order to build a complete Czech Calendar with proper sanctorale feasts and the additional temporale feast of Christ the Priest, it is necessary, apart of loading the sanctorale data, to provide a Temporale instance with the extension applied:

CR = CalendariumRomanum

year = 2016
sanctorale = CR::Data::CZECH.load
temporale =
    # the important bit: apply the Temporale extension
    extensions: [CR::Temporale::Extensions::ChristEternalPriest]

calendar =, sanctorale, temporale)

The feast of Christ the Priest, by it's nature, extends the cycle of Feasts of the Lord in the Ordinary Time and thus clearly belongs to the temporale. Even if your proper movable feast is by it's nature a sanctorale feast, just having a movable date, the only way to handle it using this gem is to write a temporale extension. There is no support for movable feasts in the Sanctorale class. Even the single movable sanctorale feast of the General Roman Calendar, the memorial of Immaculate Heart of Mary, is, by a little cheat, currently implemented in the Temporale.

Any object defining method each_celebration, which yields pairs of "date computer" and Celebration, can be used as temporale extension. Unless you have a good reason to do otherwise, a class or module defining each_celebration as class/module method is a convenient choice.

CR = CalendariumRomanum

module MyExtension
  # yields celebrations defined by the extension
  def self.each_celebration
      :my_feast_date, # name of a method computing date of the feast
        'My Feast', # feast title
        CR::Ranks::FEAST_PROPER, # rank
        CR::Colours::WHITE # colour

      # Proc can be used for date computation instead of a method
      # referenced by name
      lambda {|year| CR::Temporale::Dates.easter_sunday(year) + 9 },
        # It is possible to use a Proc as feast title if you want it
        # to be determined at runtime - e.g. because you want to
        # have the feast title translated and follow changes of `I18n.locale`
        proc { I18n.t('my_feasts.another_feast') },

  # computes date of the feast;
  # the year passed as argument is year when the liturgical
  # year in question _begun_
  def self.my_feast_date(year)
    # the day before Christ the King
    CR::Temporale::Dates.christ_king(year) - 1

temporale =, extensions: [MyExtension])

# the feast is there!
temporale.get(, 11, 25)) # => #<CalendariumRomanum::Celebration:0x0000000246fd78 @title="My Feast", @rank=#<CalendariumRomanum::Rank:0x000000019c27e0 @priority=2.8, ... >, @colour=#<CalendariumRomanum::Colour:0x000000019c31e0 @symbol=:white>>


This gem provides an executable, calendariumrom. It's handful of subcommands can be used to query liturgical calendar from the command line and to check validity of sanctorale data files.

1. Query liturgical calendar from the command line

  • calendariumrom query --calendar universal-fr 2007-06-25 queries a non-default (French) calendar for any given date. --calendar can be omitted, the default calendar (universal-en) is used then. The date can be omitted as well, calendariumrom will query the current date, then. Please note that the date has to be in format YYYY-MM-DD or YYYY/MM/DD. If the day, or even the month is omitted, query will query a whole month, or even a whole year. The specified calendar has to be one in the resulting list of the calendarium calendars command, or a valid filesystem path.
  • calendariumrom calendars will list all available data files known to calendarium-romanum.

2. Check sanctorale data files

  • calendariumrom cmp FILE1 FILE2 will load 2 data files from the file system and compare them. If there are any differences in rank or colour of corresponding celebrations, it will output them.
  • calendariumrom errors FILE1, ... finds errors in a data file. It tries to load it from file system, and if the parser will fail, for whatever reason, it will print out the reason.

3. Help

  • calendariumrom lists available subcommands
  • calendariumrom help [COMMAND] outputs a short help for all available subcommands

How to run tests

Get the sources, install development dependencies

bundle install

then execute tests with

rake spec

See also .travis.yml for comprehensive tests run on the CI.