Rails helper to render time using client's browser locale

application_helper.rb

# Use this in place of `time_tag`
# Ex: <%= local_time_tag user.created_at %>
  
def local_time_tag time, opts = {}
  opts[:data] = (opts[:data] || {}).merge format: 'local'
  opts[:title] ||= time
  time_tag(time, opts) + content_tag(:script, raw(<<-JAVASCRIPT))
    var nodes = document.querySelectorAll('time[data-format=local]');
    if (nodes.length > 0) {
      var elem = nodes[nodes.length - 1];
      var time = new Date(elem.getAttribute('datetime'));
      if (time.toLocaleString) { elem.innerHTML = time.toLocaleString() }
    }
  JAVASCRIPT
end