app/views/admin/generic/sales/_form.html.erb
<%= f.error_messages %>
<ul>
<li class="field three large-3">
<%= f.label :product_id %>
<%= f.select :product_id, products, include_blank: true %>
</li>
<li class="field three large-3">
<%= f.label :percent_off %>
<%= f.text_field :percent_off %>
</li>
<li class="field date-select">
<%= f.label :starts_at %>
<%= f.datetime_select :starts_at %>
</li>
<li class="field date-select">
<%= f.label :ends_at %>
<%= f.datetime_select :ends_at %>
</li>
</ul>