{% set total = 0 %}
{% for episode in podcast.episodes %}
    {% set total = total + episode.duration.totalMilliseconds %}
{% endfor %}

{# // is division and then rounding down (floor) #}

{% set hours   = total  // (1000 * 3600) %}
{% set minutes = (total // (1000 * 60)) % 60 %}
{% set seconds = (total // 1000) % 60 %}

{% if hours < 10 %}
    {% set hours = "0" ~ hours %}
{% endif %}

{% if minutes < 10 %}
    {% set minutes = "0" ~ minutes %}
{% endif %}

{% if seconds < 10 %}
    {% set seconds = "0" ~ seconds %}
{% endif %}

Gesamtdauer aller {{ podcast.episodes|length }} Episoden: {{ hours }} Stunden {{ minutes }} Minuten {{ seconds }} Sekunden