Japanese Calendar

Japanese calendar utility for Ruby.

Installation

Add this line to your application's Gemfile:

gem 'japanese_calendar'

And then execute:

$ bundle

Or install it yourself as:

$ gem install japanese_calendar

Usage

To get the Japanese era name, use the era_name method:

Time.new(2019,  5,  1).era_name # => "令和"
Time.new(1989,  1,  8).era_name # => "平成"
Time.new(1926, 12, 25).era_name # => "昭和"
Time.new(1912,  7, 30).era_name # => "大正"
Time.new(1873,  1,  1).era_name # => "明治"

If you want to get the Japanese era name in romaji, pass :romaji:

Time.new(2019,  5,  1).era_name(:romaji) # => "Reiwa"
Time.new(1989,  1,  8).era_name(:romaji) # => "Heisei"
Time.new(1926, 12, 25).era_name(:romaji) # => "Showa"
Time.new(1912,  7, 30).era_name(:romaji) # => "Taisho"
Time.new(1873,  1,  1).era_name(:romaji) # => "Meiji"

The following examples show how to check the Japanese era:

Time.new(2019,  5,  1).reiwa?  # => true
Time.new(1989,  1,  8).heisei? # => true
Time.new(1926, 12, 25).showa?  # => true
Time.new(1912,  7, 30).taisho? # => true
Time.new(1873,  1,  1).meiji?  # => true

You can convert to a Japanese year with the era_year method:

Time.new(2019,  5,  1).era_year # => 1
Time.new(2019,  4, 30).era_year # => 31
Time.new(1989,  1,  7).era_year # => 64
Time.new(1926, 12, 24).era_year # => 15
Time.new(1912,  7, 29).era_year # => 45

To get a string representation of the Japanese calendar, use the strftime method:

time = Time.new(2019, 5, 1)

# Japanese era
time.strftime("%JN")  # => "令和"
time.strftime("%Jn")  # => "令"
time.strftime("%JR")  # => "Reiwa"
time.strftime("%^JR") # => "REIWA"
time.strftime("%Jr")  # => "R"
time.strftime("%Jy")  # => "01"
time.strftime("%-Jy") # => "1"
time.strftime("%_Jy") # => " 1"

# Japanese weekday name
time.strftime("%JA") # => "水曜日"
time.strftime("%Ja") # => "水"

# More examples
time.strftime("%JN%-Jy年%-m月%-d日(%Ja)") # => "令和1年5月1日(水)"
time.strftime("%Jr%Jy.%m.%d")            # => "R01.05.01"
time.strftime("%B %-d, %-Y (%JR %-Jy)")  # => "May 1, 2019 (Reiwa 1)"

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/RyoYamamotoJP/japanese_calendar. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.