Can Ruby print out time difference (duration) readily?

Here's a quick and simple way to implement this. Set predefined measurements for seconds, minutes, hours and days. Then depending on the size of the number, output the appropriate string with the those units. We'll extend Numeric so that you can invoke the method on any numeric class (Fixnum, Bignum, or in your case Float).

class Numeric
  def duration
    secs  = self.to_int
    mins  = secs / 60
    hours = mins / 60
    days  = hours / 24

    if days > 0
      "#{days} days and #{hours % 24} hours"
    elsif hours > 0
      "#{hours} hours and #{mins % 60} minutes"
    elsif mins > 0
      "#{mins} minutes and #{secs % 60} seconds"
    elsif secs >= 0
      "#{secs} seconds"
    end
  end
end

Have a look at the Rails DateHelper.distance_of_time_in_words method. It will give you a great starting place. Despite being loaded with magic numbers, the approach should work for you.

There is a gem available https://rubygems.org/gems/time_diff

Which gives the difference in a hash