average_time_of_day.rb

require 'time'

def average_time_of_day(allTimes)
	times = convert_strings_to_times(allTimes)
	average_time = compute_average_time(times)
	return format_time(average_time)
end

def convert_strings_to_times(strings)
	times = strings.map do |str|
		time = Time.parse(str)

		# "AM" dates should be consided one day after "PM" dates
		time += 60 * 60 * 24 if str =~ /am/

		time
	end

	times
end

def compute_average_time(times)
	times_as_integer = times.map { |time| time.to_i }

	mean = times_as_integer.inject('+') / times_as_integer.length

	return Time.at(mean)
end

def format_time(time)
	time.strftime("%I:%M%P").gsub(/^0/, "")
end

TestAverageTimeOfDay.rb

require 'test/unit'
require 'average_time_of_day'

class TestAverageTimeOfDay < Test::Unit::TestCase
	def test_multiple_times
		assert_equal("5:59pm", average_time_of_day(["11:58pm", "12:00pm"]))
		assert_equal("6:51am", average_time_of_day(["6:41am", "6:51am", "7:01am"]))
		assert_equal("12:01am", average_time_of_day(["11:51pm",  "12:06am", "12:01am","11:56pm", "12:11am"]))
	end

end