blist.rb

raise 'Usage: ruby blist.rb "[H]H:MM AM|PM" "[H]H:MM AM|PM"' unless ARGV.length == 2

def parse_date(date_str)
  time, meridiem = date_str.split(/\s+/)
  hour, minute = time.split(/:/).map{|i| i.to_i}
  hour += 12 if meridiem == "PM"
  hour = 0 if meridiem == "AM" && hour == 12
  {:time => "#{hour}:#{minute}", :hour => hour, :minute => minute}
end

one, two = parse_date(ARGV[0]), parse_date(ARGV[1])
degrees = (two[:time] > one[:time] ?
           two[:hour] - one[:hour] :
           24 - one[:hour] + two[:hour]) * 360
degrees += (two[:minute] - one[:minute]) / 60 * 360
puts degrees