jekyll: Invalid Date: '' is not a valid datetime - ruby

Question

I am new to jekyll:
So far I had done what the tutorial has mentioned: This is what I have in _layout: post.html file:
---
layout: default
---
<div class="post">
<h1>{{ page.title }}</h1>
<span class="post-date">{{ page.date | date_to_string }}</span>
{{ content }}
</div>
<div class="related">
<h2>Related Posts</h2>
<ul class="related-posts">
{% for post in site.related_posts limit:3 %}
<li>
<h3>
<a href="{{ post.url }}">
{{ post.title }}
<small>{{ post.date | date_to_string }}</small>
</a>
</h3>
</li>
{% endfor %}
</ul>
</div>
and I use md file with a name 2014-01-01-myNewPost.md and I get the following error:
Generating... Invalid Date: '' is not a valid datetime.
Liquid Exception: exit in _layouts/post.html
I don't seem to see any issues but unable to really figure it out why its not working.

Answer 1

My problem was that for some reason I kept getting this error in the terminal when I ran "jekyll serve --incremental":
Liquid Exception: Invalid Date: 'nil' is not a valid datetime. in /_layouts/post.html
ERROR: YOUR SITE COULD NOT BE BUILT:
------------------------------------
Invalid Date: 'nil' is not a valid datetime.
and after much digging, it's because jekyll picks up posts of any kind in the root directory, even if they are in a whole different folder. I had my posts in "_posts" and my test posts in "old_posts".
Just having the "old_posts" directory at the root project level made this error occur. Make sure you don't have anything like that.

Answer 2

Most likely, you have moved the sample posts to another directory, e.g., examples. Jekyll finds the posts there and tries to process them, which leads to the encountered problem.
Add the examples folder to the exclude list in _config.yml, and Jekyll will start as expected.

Answer 3

Seems like you've a typo in the date variable in your post YAML matter. Check if your post date complies with this format YYYY-MM-DD HH:MM:SS
I've checked the post layout code posted above, its fine.
If nothing works, uninstall Jekyll and install the last stable release 1.2.1 by running these commands
~ $ gem uninstall jekyll
~ $ gem install jekyll --version(="1.2.1")

Answer 4

I had this happen and it turns out I had duplicated a file from my _posts directory by mistake with option-click and it was sitting in the root of my site. Would be nice if the processor would give a detailed description about the cause of the error in addition to the general error message.

Answer 5

Based on this GitHub issue it looks like Jekyll will complain if you label something as a post and then try to format the date if that thing doesn't have a date in the title or front matter. This doesn't happen if you reference {{ page.date }} without formatting it, so it must be some kind of nil error in the format function.
I just had this problem and I realized I'd labeled a bunch of static pages with layout: post in the front matter when the filename was example.md rather than 2016-01-01-example.md. I changed those files to layout: page and that solved the problem.
So at least on my site I have to make sure things without dates are pages and things with dates are posts. (I removed the date from my posts layout when I redesigned the site and just now got around to trying to put it back.)