Form select entries by year For example have the following code:

&lt;form action=""&gt;
       &lt;select&gt;
               &lt;option&gt;2015&lt;/option&gt;
               &lt;option&gt;2014&lt;/option&gt;
               &lt;option&gt;2013&lt;/option&gt;
               &lt;option&gt;2012&lt;/option&gt;
      &lt;/select&gt;

      &lt;input type="submit" value="select"&gt;
&lt;/form&gt;


how to get a entries of the selected year?
First thing I recommend is to read through the Search Form guide from the Craft documentation.
To explain the rest I'll add some comments to the example code.

form.html

{# Use the `group` filter to get the years, entries were posted in #}
{% set entries = craft.entries.section('news') %}
{% set entriesByYear = entries|group('postDate|date("Y")') %}

&lt;select name="year"&gt;

    {# Go through the `year` groups #}
    {% for year, entries in entriesByYear %}
        &lt;option value="{{ year }}"&gt;{{ year }}&lt;/option&gt;
    {% endfor %}

&lt;/select&gt;


results.html

{# Get the params #}
{% set year = craft.request.getParam('year') %}

{# Compose a param in this format: 'and, &gt;= 2014-01-01, &lt; 2015-01-01' #}
{% set dateParam = 'and, &gt;= ' ~ year ~ '-01-01, &lt; ' ~ (year + 1) ~ '-01-01' %}

{# Query and loop through the entries #}
{% set entries = craft.entries.section('news').postDate(dateParam) %}

{% if entries|length %}
    ...
{% endif %}