{% set year = 0 %}

{% for talk in data.talks if date(talk.date) < date('today') %}
    {% if loop.first %}
        <h2>Previous Talks</h2>
    {% endif %}

    {% if talk.date|date('Y') != year %}
        {% set year = talk.date|date('Y') %}

        </ul>
        <h3>{{ year }}</h3>
        <ul>
    {% endif %}

    <li>
        {{- include('talk-listing-item') -}}
    </li>
{% endfor %}

{% if year != 0 %}
    </ul>
{% endif %}