add_week
Adds a week to a date. The value must be of the form {{Y,M,D},{H,I,S}}.
For example:
{{ value|add_week }}
When the value is {{2008,12,10},{15,30,0}}, the output is {{2008,12,17},{15,30,0}}.
The filter has an optional argument which defines the number of weeks to add:
{{ value|add_week:4 }}
When the value is {{2008,12,10},{15,30,0}}, the output is {{2009,1,7},{15,30,0}}.