expected Hash (got String) for param `date' error with pickadate in rails

_form.html.erb

<%= form_for(@event, :html => { class: 'form-horizontal'}) do |f| %>

  <%= f.label :title %>
  <%= f.text_field :title %>

  <%= f.label :time %>
  <%= f.text_field :time, class: "timepicker" %>

  <%= f.label :date %>
  <%= f.text_field :date, class: "datepicker" %>

  <%= f.submit 'Continue', class: "btn btn-primary" %>
<% end %>

schema.rb

t.string   "time"
t.date     "date"