Add comma between dates

_layouts/post.html

@@ -43,7 +43,7 @@
                     <h4 class="entry-title">
                       <a href="{{ post.url }}">{{ post.title }}</a>
                     </h4>
-                    <p class="entry-date">{{ post.date | date: "%B %-d %Y" }}</p>
+                    <p class="entry-date">{{ post.date | date: "%B %-d, %Y" }}</p>
                   </div>
                 </div>
               </div>

index.html

@@ -13,7 +13,7 @@ title: "Home"
       <h2 class="entry-title">
         <a href="{{ post.url }}">{{ post.title }}</a>
       </h2>
-      <p class="entry-date">{{ post.date | date: "%B %-d %Y" }}</p>
+      <p class="entry-date">{{ post.date | date: "%B %-d, %Y" }}</p>
     </div>
   </div>
 {% endfor %}