Setting relative date with moment.js

application.js

//= require jquery
//= require jquery_ujs
//= require turbolinks
//= require moment
//= require_tree .

item.js.coffee

timeElements = document.querySelectorAll('[data-behavior~=relative_date]')
  
for el in timeElements
  el.moment = moment(el.getAttribute('datetime')
  el.update = -> @innerText = @moment.fromNow()
  el.update()
  
setInterval (-> el.update() for el in timeElements), 60000

items_helper.rb

module ItemsHelper
  def relative_date(date)
    options = { datetime: date.iso8601, data: { behavior: 'relative_date' } }
    content_tag :time, options do
      "#{time_ago_in_words(date)} ago"
    end
  end
end

show.html.erb

Created <%= relative_date @item.created_at %>