How I can sort my entry that belong to 3 section on date? {% set blog = craft.entries.section('blog').all() %}
{% set news = craft.entries.section('news').all() %}
{% set caseStudies = craft.entries.section('caseStudies').all() %}
{% set allEntries = blog|merge(news)|merge(caseStudies) %}
{% for entry in allEntries %}  
 &lt;span&gt;  
       {{entry.nameSection}} | {{entry.dateNews|date("F  d, Y")}}
&lt;/span&gt;
&lt;h3 class="title post-title"&gt;
      {{entry.title}}
&lt;/h3&gt;
{% endfor %}
Try chaining the sections together like:

{% set allEntries = craft.entries({
  section: ['blog', 'news', 'caseStudies']
}).orderBy('elements.dateCreated asc').all() %}


Then

{% for entry in allEntries %}  
   &lt;span&gt;  
       {{entry.nameSection}} | {{entry.dateNews|date("F  d, Y")}}
   &lt;/span&gt;

   &lt;h3 class="title post-title"&gt;
       {{entry.title}}
   &lt;/h3&gt;
{% endfor %}