CODE EXAMPLE FOR RUBY

liquid add date

{% assign date = '2015-04-20' | date: '%s' %}
{% assign seconds = 5 | times: 24 | times: 60 | times: 60 %}
{{ date | date: "%s" | plus: seconds | date: "%Y-%m-%d" }}


{% assign seconds = 5 | times: 24 | times: 60 | times: 60 %}
{{ 'now' | date: "%s" | plus: seconds | date: "%Y-%m-%d" }}

{{ date | date: "%s" | plus: 86400 | date: "%d/%m/%Y"   }}