Format date field in twig
In Twig, drill down to the timestamp value:

node.html.twig:

{{ content.field_name['#items'].value | date('F d, Y') }}


For a loop, do:

{% for items in content.field_name['#items'] %}
  {{ items.value | date('F d, Y') }}
{% endfor %}


field.html.twig:

{% for item in items %}
  {{ item.content["#markup"] | date('F d, Y') }}
{% endfor %}


Note: Set field format display option to plain or custom if using the field template. This field option can break your site just by someone changing the format option for the field, so use caution.