diff --git a/app/assets/stylesheets/sidebar_admin.css.scss b/app/assets/stylesheets/sidebar_admin.css.scss
index 727a40f7b..d86b9ff4c 100644
--- a/app/assets/stylesheets/sidebar_admin.css.scss
+++ b/app/assets/stylesheets/sidebar_admin.css.scss
@@ -33,4 +33,4 @@
     right: 20px;
     display: inline-block;
   }
-}
+}
\ No newline at end of file
diff --git a/lib/archives_sidebar/app/views/archives_sidebar/_content.html.erb b/lib/archives_sidebar/app/views/archives_sidebar/_content.html.erb
index 7d74c3347..2fbf66c8c 100644
--- a/lib/archives_sidebar/app/views/archives_sidebar/_content.html.erb
+++ b/lib/archives_sidebar/app/views/archives_sidebar/_content.html.erb
@@ -1,11 +1,11 @@
 <% unless sidebar.archives.blank? %>
-  <h3 class="sidebar_title"><%= sidebar.title %></h3>
-  <div class="sidebar_body">
+  <h3 class="sidebar-title"><%= sidebar.title %></h3>
+  <div class="sidebar-body">
     <ul id="archives">
       <% sidebar.archives.each do |month| %>
         <% counter = sidebar.show_count ? "<em>(#{month[:article_count]})</em>" : "" %>
         <li>
-          <%= link_to"#{month[:name]} #{counter}".html_safe,  articles_by_month_path( month[:year], "%02i" % (month[:month]+1) ) %>
+          <%= link_to"#{month[:name]} #{counter}".html_safe,  articles_by_month_path( month[:year], "%02i" % (month[:month])) %>
         </li>
       <% end %>
     </ul>
diff --git a/lib/archives_sidebar/lib/archives_sidebar.rb b/lib/archives_sidebar/lib/archives_sidebar.rb
index b77559ca6..9a5e879cb 100644
--- a/lib/archives_sidebar/lib/archives_sidebar.rb
+++ b/lib/archives_sidebar/lib/archives_sidebar.rb
@@ -30,11 +30,11 @@ def parse_request(_contents, _params)
     article_counts = Content.find_by_sql(["select count(*) as count, #{date_func} from contents where type='Article' and published = ? and published_at < ? group by year,month order by year desc,month desc limit ? ", true, Time.now, count.to_i])
 
     @archives = article_counts.map do |entry|
-      month = (entry.month.to_i%12)+1
+      month = (entry.month.to_i%13)
       year = entry.year.to_i
       {
         name: I18n.l(Date.new(year, month), format: '%B %Y'),
-        month: month - 1,
+        month: month,
         year: year,
         article_count: entry.count
       }