{%  macro ageFromDateTimeString(dateTimeString) %}
  {% set dateString = dateTimeString.split("T")[0] %}
  {% set dateParts = dateString.split("-") %}
  {% set birthdayYear = dateParts[0] %}
  {% set birthdayMonth = dateParts[1] %}
  {% set birthdayDay = dateParts[2] %}
  {% set todayYear = date_now.getFullYear() %}
  {% set todayMonth = date_now.getMonth() + 1 %}
  {% set todayDay = date_now.getDate() %}
  {% set age = todayYear - birthdayYear %}

  {% if todayMonth < birthdayMonth %}
    {% set age = age - 1 %}
  {% elif (todayMonth == birthdayMonth) and (todayDay < birthdayDay) %}
     {% set age = age - 1 %}
  {% endif %}

  {{ age }}
{% endmacro %}