Takes pairs of time and returns total seconds for the duration of pairs and a parsed version of the whole duration

io.rb

require 'time'

class Io

  def self.get_duration(array)
    # only evaluate if there are an even number of items in the array
    if array.length.even?
      # iterate through each argument
      i_ary = []
      array.each do |arg|
        # parse arg as seconds since unix epoch
        i_ary << Time.parse(arg).to_i
      end
      diff_ary = []
      i_ary.each_with_index do |s, i|
        if i.even? && s != i_ary.last
          diff = i_ary[i + 1] - s
          diff_ary << diff
        end
      end
      sum = diff_ary.inject(:+)
      mm, ss = sum.divmod(60)
      hh, mm = mm.divmod(60)
      puts " >> %d hours, %d minutes and %d seconds" % [hh, mm, ss]
      puts " >> " + sum.to_s + " seconds"
    else
      raise
    end
  end
end

puts "Enter times, e.g. 8:30 AM, 9:30 AM, etc..."
times = gets.chomp.split(',')
if times.length.odd?
  puts "You must enter an even number of times as comma separated values. Please try again."
  exit(false)
end
Io.get_duration(times)
exit(true)