Iterate over a list of posts and compare the date - jekyll

Question

This is my markup for the list view of posts:
<ul class="eventlist">
{% for post in site.posts reversed %}
<li class="eventlist-element">
{% if post.href %}
<a class="eventlist-element__link" href="{{ post.href }}">
{% else %}
<a class="eventlist-element__link" href="{{ post.url | prepend: site.baseurl }}">
{% endif %}
<time datetime="{{ post.date | date: "%Y-%m-%d" }}"class="eventlist-element__date">
<span class="eventlist-element__date-day">{{ post.date | date: "%d" }}</span>
<span class="eventlist-element__date-day-name">{{ post.date | date: "%a" }}</span>
</time>
<div class="eventlist-elemnt-infowrap">
<span class="eventlist-element__title">{{ post.title }}</span>
<span class="eventlist-element__venue">{{ post.venue }}</span><span class="eventlist-element__time">{{ post.time }}</span><span class="eventlist-element__ticket">{{ post.ticket }}</span>
</div>
<span class="eventlist-element__bullets"></span>
</a>
</li>
{% endfor %}
</ul>
I want to iterate over all posts and want to compare the post.date. If we have let's say 3 posts on the same day I want markup a for post 1 and for post 2 and 3 markup b. I've tried a few things but nothing worked so far.

Answer 1

Try something along these lines:
{% assign previousDate = site.date %}
{% for post in site.posts %}
{% if post.date == previousDate %}
// some other class
{% endif %}
{% assign previousDate = post.date %}
{% endfor %}
Basically you assign the date of the previous post to some variable and compare it with the current posts date. If they are the same you apply a different style. Not sure if you can use date as is, does it also contain hours, minutes,..? If so you will want to filter it to get out only the year, month, day.

Answer 2

Some code :
{% assign defaultStyle = 'defaultStyle' %}
{% assign alternateStyle = 'alternateStyle' %}
{% assign counter = 1 %}
{% for post in site.posts %}
{% if previousPostDate %}
{% if previousPostDate == post.date %}
{% capture counter %}{{ counter | plus: 1 }}{% endcapture %}
{% else %}
{% assign counter = 1 %}
{% endif %}
{% endif %}
{% if counter | to_number > 1 %}
{% assign defaultStyle = alternateStyle %}
{% endif %}
<div class="{{ defaultStyle }}">
<h3>{{ post.title }}</h3>
<p>{{ post.date }}</p>
</div>
{% assign previousPostDate = post.date %}
{% endfor %}
The code implements :
If I'm not the first post in a date group my style is different.
Your logic was
If I'm not the first post in a date group of three posts (or more) my style is different.
The part date group of three posts or more implies that you already know how many "same date posts" you have and makes the code more complex.