Requires ruby 2.1+. Released under the MIT license. `colorize` gem is optional, but adds colors. Example output: https://i.imgur.com/BmtAoXc.png

woomy.rb

#!/usr/bin/env ruby
# -*- encoding: UTF-8 -*-

#######################################################################
# woomy.rb prints the current Splatoon map rotations.                 #
# If the `colorize` gem is installed, it will print them with colors. #
#######################################################################

=begin
Copyright (c) 2015+ Morgan Jones

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
=end

require 'uri'
require 'net/http'
require 'json'
begin
  require 'colorize'
rescue LoadError => e
  STDERR.puts "#$0: error loading colorize, your terminal output won't be as fresh" if $VERBOSE
end

module Woomy
  BOOYAH_BASE = URI('https://splatoon.ink/schedule.json').freeze
  module Refinements
    refine String do
      def method_missing method, *args, &block
        self
      end
    end

    refine Numeric do
      def ms
        Time.at self / 1000, (self % 1000) * 1000
      end

      def duration
        ret = []
        val = self
        hours = (val / 3600).floor
        val %= 3600
        minutes = (val / 60).floor
        val %= 60
        seconds = val.floor
        ret << "#{hours} #{hours == 1 ? 'hour'.freeze : 'hours'.freeze}" if hours > 0
        ret << "#{minutes} #{minutes == 1 ? 'minute'.freeze : 'minutes'.freeze}"
        ret << "#{seconds} #{seconds == 1 ? 'second'.freeze : 'seconds'.freeze}"
        ret.join ', '.freeze
      end
    end

    refine Time do
      def format
        self.strftime '%F %T'.freeze
      end
    end
  end

  module Version
    VERSION = '0.2'.freeze
    NAME = Woomy.to_s.freeze
    IDENT = "#{NAME} #{VERSION}".freeze
    AGENT = '3'.freeze
  end

  include Version
end

# Activate the refinements
using Woomy::Refinements

begin
  # Make the request
  req = Net::HTTP::Get.new Woomy::BOOYAH_BASE
  req['User-Agent'.freeze] = Woomy::AGENT
  req['Accept'.freeze] = 'application/json; charset=UTF-8'.freeze
  req['X-Requested-With'.freeze] = Woomy::IDENT
  res = Net::HTTP.start(Woomy::BOOYAH_BASE.hostname, Woomy::BOOYAH_BASE.port,
                        use_ssl: Woomy::BOOYAH_BASE.scheme == 'https'.freeze) {|h| h.request(req)}

  if res.is_a? Net::HTTPSuccess
    # Parse the schedule
    schedule = JSON.parse res.body, symbolize_names: true
    now = Time.now
    update_time = schedule[:updateTime].ms
    cur_start, cur_end = nil, nil

    # Print each item
    language = ENV['LANG'].to_s =~ /ja/ ? :jp : :en
    schedule[:schedule].each do |item|
      # Get start and end time
      start_time = item[:startTime].ms
      end_time = item[:endTime].ms
      STDOUT.print "From #{start_time.format.yellow} to #{(end_time - 1).format.blue}:"
      if now >= start_time and now < end_time
        cur_start, cur_end = start_time, end_time
        STDOUT.print " #{'<:='.white.on_magenta}"
      end
      STDOUT.puts

      # Print each mode for this slot
      item[:modes].each do |mode|
        maps = mode[:maps].map {|a| a[:name][language]}
        rules = mode[:rules][language]
        color = case mode[:rules][:en]
                when /Splatfest/i then :light_blue
                when /Turf War/i then :green
                when /Rainmaker/i then :blue
                when /Tower Control/i then :magenta
                when /Splat Zones/i then :cyan
                else :white
                end
        STDOUT.puts "  >> #{rules.colorize(color)}: #{maps.join '; '.freeze}"
      end
    end

    # Print the footer
    STDOUT.puts "It's #{now.format.light_magenta}. Updated at #{update_time.format.light_magenta}."
    if !cur_start.nil? and !cur_end.nil?
      STDOUT.puts "#{(cur_end - now).duration.magenta} left in map rotation. "
    end

    exit 0
  else
    # Problem with the response
    raise "got HTTP #{res.code} from #{Woomy::BOOYAH_BASE}"
  end
rescue => e
  # Issue with something; catch it and exit with a meaningful error code
  STDERR.puts "#$0: #{e.class}: #{e.message}"
  STDERR.puts e.backtrace
  exit 1
end