tishogeorgiev.rb

#!/usr/bin/env ruby

require 'time'
require 'date'

# The method assumes that the times given are in order
# of earliest to latest.
def average_time_of_day(times)
  
  # Holds the last DateTime object we looked at to compare with.
  # 0 gives us a nice starting point, since a new DateTime
  # will always be > 0.
  previous_time = 0
  
  average = times.inject(0.0) do |sum, time_as_string|
    time = DateTime.strptime(time_as_string, '%I:%M%p')
    
    # If the parsed time happens to be earlier than the last one 
    # we looked at, loop until we've caught up.
    time += 1 while time < previous_time
    previous_time = time
    
    # A very simple DateTime => Time conversion, so we can a to_i
    sum + Time.parse(time.to_s).to_i
  end / times.length
  
  Time.at(average).utc.strftime('%I:%M%p').downcase
end

# Should equal 12:01am
puts average_time_of_day(["11:51pm", "11:56pm", "12:01am", "12:06am", "12:11am"])

# Should equal 6:51am
puts average_time_of_day(["6:41am", "6:51am", "7:01am"])

# Works even with times that are a day apart.
# In the following example we'll start at today's date and end
# with a date that's two days from now.
# Should equal 11:35pm
puts average_time_of_day(["6:15am", "12:15pm", "6:15pm", "12:15am", "6:15am", "2:15am"])