Jekyll Mark Old Posts

With technology changing so rapidly and people in such a big hurry, sometimes older suggestions or out of date recommendations are the first things that programmers run into. You know you’ve fallen for it - a quick google search and you get your first result and you give it a shot; never mind that it’s a blog entry from 7 years ago.

Now, I would argue that that’s your fault - you should be keeping an eye on the date. But, I’ve decided that the best thing to do for visitors is to remind them that this content is older.

When I was using WordPress, I made a plugin called Label Old Posts - but now I use Jekyll for my blog. I could go the route of making a plugin, but you’d still have to use some sort of ‘shortcode’ type syntax to get the notification in the proper location in your theme. Instead, I decided to just add code to my post template.

Here’s the liquid code:

{% capture now %}{{'now' | date: '%s'}}{% endcapture %}  
{% capture postDate %}{{page.date | date: '%s'}}{% endcapture %}  
{% assign difference = now | minus: postDate %}  
{% if difference > 47340000 %}  
  <div class="old-post">  
    This post is more than 18 months old. Since technology changes to rapidly, 
    this content <em>may</em> be out of date (but that's not always the case).  
    Please remember to verify any technical or programming information
    with the current release.
  </div>  
{% endif %}

First, capture the current date and the post date as unix timestamps. Then, do a calculation to figure out the difference. I’m using a separate variable here because it makes it easier to do math, comparison, and it converts nicely to an integer from a string. Finally, compare the difference to the number of seconds in 18 months. If the difference is greater, display a message.