add_month
Adds a month to a date. The value must be of the form {{Y,M,D},{H,I,S}}.
For example:
{{ value|add_month }}
When the value is {{2008,12,10},{15,30,0}}, the output is {{2009,1,10},{15,30,0}}.
The filter has an optional argument which defines the number of months to add:
{{ value|add_month:3 }}
When the value is {{2008,12,10},{15,30,0}}, the output is {{2009,3,10},{15,30,0}}.