# For http://rubylearning.com/blog/2009/10/08/rpcfn-average-arrival-time-for-a-flight-2/
# I take the lazy approach and assume 12:01am is today, not tomorrow.
 
def average_time_of_day(ary)
  sec = ary.map do |t|
    hour, min_with_noonside = t.split(":")
    (hour.to_i * (min_with_noonside.include?("pm") ? 2 : 1) * 3600) + (min_with_noonside.to_i * 60)
  end.inject(0) { |s,c| s += c } / ary.size
  hour = sec / 3600
  min = ((sec - hour * 3600) / 60).to_s
  min += hour > 12 ? "pm" : "am"
  hour -= 12 if hour > 12
  "#{hour}:#{min}"
end