Count distinct by date

I think I figure out the proper way to do it. Thanks Mark for pointing out the 1 day condition in my query:

{
"query": { "term": { "username": { "value": "guest@bdtt" } } },
"aggs": {
"sessions": {
    "terms" : { "field" : "callingstationid" },
    "aggs": {
        "total_minute": {
            "sum": {"script":"doc['acctstoptime'].date.getMillis() - doc['acctstarttime'].date.getMillis()"}
        },
        "count_starttime": {
	    	"cardinality" : 
	            {"script":"doc['acctstarttime'].date.dayOfMonth"}
		}
    }
}

}
}