snippet for formatted dates...

_drug_fields.html.erb

<tr class="nested-fields">
  #How do I use strftime on the drug date field below?
  <td><%= f.input :drug_date, as: :string, label: false, :input_html => { class: 'ui-date-picker' } %></td>
  <td><%= f.input :drug, label: false %></td>
  <td><%= f.input :drug_amount, label: false %></td>
  <td><%= f.input :drug_problem, label: false %></td>
  <td><%= f.input :drug_administrator, label: false %></td>
  <td><%= link_to_remove_association "remove", f, class: "btn btn-primary btn-sm" %></td>
</tr>

_form.html.erb

<%= f.fields_for :drugs do |drug| %>
  <%= render 'drug_fields', f: drug %>
<% end %>