scinote-web/app/views/project_comments/_list.html.erb

<% day = 0 %>
<% current_day = days_since_1970(DateTime.current) %>
<% comments.each do |comment| %>
  <% comment_day = days_since_1970(comment.created_at) %>
    <% if comment_day <= current_day && comment_day > day %>
      <% day = days_since_1970(comment.created_at) %>
      <li class="comment-date-separator">
        <p class="text-center"><%= l(comment.created_at, format: :full_date) %></p>
      </li>
     <% end %>
  <li class="comment">
    <%= render 'project_comments/comment.html.erb', comment: comment %>
  </li>
<% end %>