Jekyll custom date - yaml

Question

I want use bellow code to display custom date in my Jekyll site
{% assign m = page.date | date: "%-m" %}
{% case m %}
{% when '1' %}Januar
{% when '2' %}Februar
{% when '3' %}März
{% when '4' %}April
{% when '5' %}Mai
{% when '6' %}Juni
{% when '7' %}Juli
{% when '8' %}August
{% when '9' %}September
{% when '10' %}Oktober
{% when '11' %}November
{% when '12' %}Dezember
{% endcase %}
But I don't now where to put it (I tried in post.html but does not work)

Answer 1

I've made a template for this.
This template translate a date in a specific language. Here it's french but feel free to change month and day arrays.
This template can be used in an enumeration of post/page (eg: the index page) or in a post/page template.
When used in an enumeration, you need to pass the date to process
{% for post in site.posts %}
<li>
<span class="post-date">{% include custom_date_full_fr.html date = post.date %}</span>
<a class="post-link" href="{{ post.url | prepend: site.baseurl }}">{{ post.title }}</a>
</li>
{% endfor %}
Where used in a page/post template, you just have to include the template, as the page.date will already be available.
{% include custom_date_full_fr.html %}
custom_date_full_fr.html
{% if include.date %}
{% assign processed_date = include.date %}
{% else if page.date %}
{% assign processed_date = page.date %}
{% endif %}
{% comment %}-------- Test if we have a date to process --------{% endcomment %}
{% if processed_date %}
{% assign month = "janvier,février,mars,avril,mai,juin,juillet,août,septembre,octobre,novembre,décembre" | split: "," %}
{% comment %}------ Note : sunday is the first day in this array -------{% endcomment %}
{% assign day = "dimanche,lundi,mardi,mercredi,jeudi,vendredi,samedi" | split: "," %}
{% assign month_index = processed_date | date: "%m" | minus: 1 %}
{%comment%}----------------------------------------------
Here **minus: 0** is a trick to convert day_index from string to integer and then use it as an array index.
----------------------------------------------{%endcomment%}
{% assign day_index = processed_date | date: "%w" | minus: 0 %}
{%comment%}-------- Output the date ----------{%endcomment%}
{{ day[day_index] }} {{ processed_date | date: "%d" }} {{ month[month_index] }} {{ processed_date | date: "%Y" }}
{% endif %}
See here for more info :
Jekyll Date Formatting Examples by Alan W. Smith
Liquid documentation - date filters