Creating a date facet with month and day

It seems that the value of month and day are ignored (only the year value is indexed) when I create some date facets on the following admin page:
http://catalog.lib.kyushu-u.ac.jp/admin/xc/index/facets/add

Although we have defined acquisitionDate_df, date_df, and local__acquisitionDate_dt by this way, all of the values of these facets are created as the format of "YYYY-01-01T00:00:00Z".
=> see attached "drupal_toolkit_solr_screenshot.png"

The purpose of using this is to limit search results by recent acquisitions, a day ago, recent 1 week, recent 3 weeks and ...
http://catalog.lib.kyushu-u.ac.jp/en/xc/search/*?filter[3]=acquisitionDa...

Does anyone have a solution of how I can create a date facet with month and day?

Thanks.