availability_tz_convert.rb

#!/usr/bin/env ruby

# require 'pathname'
require 'active_support/all' # DateTime

# M 2025-01-13 09-18
# T 2025-01-14 07-16
# W 2025-01-15 09-18 ?
# R 2025-01-16 y


tz_os = DateTime.now.offset

filepath = ARGV[0]
target_tz = ARGV[1]

line_re = %r"(\d{4}[-]\d{2}[-]\d{2})\s+((\d{2})[-](\d{2}))"

local =
  Pathname.new(filepath)
    .readlines
    .map(&:chomp)
    .map {|line|
      line.match(line_re)
    }
    .reject(&:nil?)
    .map {|m|
      date = m[1]

      [m[3], m[4]]
        .map {|hour|
          DateTime
            .parse("#{date} #{hour}:00")
            .change(offset: tz_os)
        }
    }

remote =
  local
    .map {|times|
      times.map{|time| time.in_time_zone(target_tz)}
    }

def date_str(dt)
  dt.strftime("(#{dow_str(dt)}) %Y-%m-%d")
end

def time_str(dt)
  dt.strftime('%l %p')
end

def date_and_time_str(dt)
  [
    date_str(dt),
    time_str(dt),
  ]
    .join(" ")
end

def dow_str(dt)
  %w[
    Sun
    Mon
    Tue
    Wed
    Thu
    Fri
    Sat
  ][dt.strftime("%w").to_i]
end

puts "Timezone: #{target_tz}"
remote.each do |(start, finish)|
  print date_and_time_str(start)
  print "  to  "

  if start.day == finish.day
    print time_str(finish)
  else
    print date_and_time_str(finish)
  end

  puts
end