SolrJ has some classes which simplify access to JSON Faceting responses. These classes parse the response and maintain a Map of facet names to their values. Currently, this section has a bug where it only records stat facets in this Map if the facet value is a Number. (When writing this code, I mistakenly assumed that stat functions could be used on date fields).
We should fix JsonFacetingResponse so that it handles date-based facets correctly.