%form.post{ action: @post.new_record? ? '/admin/new' : "/admin/edit/#{@post.id}", method: 'post' }
  = form_field @post, :title, placeholder: "Title of your post."
  = form_field @post, :link, placeholder: "Optional link to external URL."
  = form_field @post, :body, type: :textarea, placeholder: "Your post's body of text. Markdown formatting available."
  = form_field @post, :summary, placeholder: "An optional summary of your post. Markdown formatting available."
  = form_field @post, :read_more, label: "'Read More' Link Text", placeholder: "When supplying a summary text, this will be the link to the full post."

  .row
    .four.columns
      = form_field @post, :slug, label: 'URL Slug', placeholder: "Your post's URL slug.", hint: @post.previous_slugs.any? ? "Previous slugs: #{@post.previous_slugs.join ', '}" : nil
    .four.columns
      = form_field @post, :published_at, placeholder: 'You can use natural language. Try "now", "tomorrow", "next Monday".'
    .four.columns
      = form_field @post, :status, type: :dropdown, options: [[:draft, "Draft"], [:published, "Published"]]

  .row
    .buttons.twelve.columns
      %input{ type: 'submit', value: @post.new_record? ? 'Create Post' : 'Update Post' }

%form.post{ action: @post.new_record? ? '/admin/new' : "/admin/edit/#{@post.id}", method: 'post' }
  = form_field @post, :title, placeholder: "Title of your post."
  = form_field @post, :link, placeholder: "Optional link to external URL."
  = form_field @post, :body, type: :textarea, placeholder: "Your post's body of text. Markdown formatting available."
  = form_field @post, :summary, placeholder: "An optional summary of your post. Markdown formatting available."
  = form_field @post, :read_more, label: "'Read More' Link Text", placeholder: "When supplying a summary text, this will be the link to the full post."

  .row
    .four.columns
      = form_field @post, :slug, label: 'URL Slug', placeholder: "Your post's URL slug.", hint: @post.previous_slugs.any? ? "Previous slugs: #{@post.previous_slugs.join ', '}" : nil
    .four.columns
      = form_field @post, :published_at, placeholder: 'Try "now", "in 3 days", ...'
    .four.columns
      = form_field @post, :status, type: :dropdown, options: [[:draft, "Draft"], [:published, "Published"]]

  .row
    .buttons.twelve.columns
      %input{ type: 'submit', value: @post.new_record? ? 'Create Post' : 'Update Post' }

Make published_at form field placeholder shorter.
Make published_at form field placeholder shorter.