Facet pivot provide hierarchical support for computing data used to populate a treemap or similar visualization. TreeMaps usually offer users extra information by applying an overlay color on top of the existing square sizes based on hierarchical counts. This second count is based on user choices, representing, usually with gradient, the proportion of the square that fits the user's choices.
The proposition is to use local parameters to specify facet query to apply for pivot which matches a tag set on facet query. Parameter format would look like:
somedate:[NOW-1YEAR TO NOW]