diff --git a/_docs/10-posts.md b/_docs/10-posts.md
index 0f65344b..9e543bae 100644
--- a/_docs/10-posts.md
+++ b/_docs/10-posts.md
@@ -2,13 +2,20 @@
 title: "Working with Posts"
 permalink: /docs/posts/
 excerpt: "Suggestions and Front Matter defaults for working with posts."
-modified: 2016-06-16
+modified: 2016-07-20T08:17:57-04:00
 ---
 
 {% include base_path %}
 
 Posts are stored in the `_posts` directory and named according to the `YEAR-MONTH-DAY-title.MARKUP` format as per [the usual](https://jekyllrb.com/docs/posts/).
 
+Where `YEAR` is a four-digit number, `MONTH` and `DAY` are both two-digit numbers, and `MARKUP` is the file extension representing the format used in the file. For example, the following are examples of valid post filenames:
+
+```
+2016-07-20-writing-jekyll-posts.md
+2015-01-03-static-site-generators.markdown
+```
+
 **Recommended Front Matter Defaults:**
 
 ```yaml