human readable time differences without dependencies

time_in_words.rb

def td_in_words(s, skip: 1)
  words = [['years',0], ['months',1], ['days',1], ['hours',0], ['minutes',0], ['seconds',0]]
  vals = (Time.mktime(0)+s).strftime("%Y %m %d %H %M %S").split(' ').map(&:to_i)
  skip.times{ words.pop && vals.pop }
  str = vals.zip(words).select{|v,(w,n)| v!=n}.map{|v,(w,n)| [v-n, (v-n)==1 ? w[0..-2] : w]}.map{|v,w| "#{v} #{w}"}.join(' ')
  str = "0 #{words.last[0]}" if str.empty?
  str
end

#usage: 
some_time_in_the_past = Time.now - 12345 * 6789
some_time_in_the_future = Time.now + 654 * 321
puts td_in_words(Time.now - some_other_time) + ' ago'
puts td_in_words(some_time_in_the_future - Time.now) + ' from now'