Date histogram response - Elasticsearch 7.9.3

{
    "aggregations":{
        "nested#my_histo_nested":{
            "doc_count":6,
            "date_histogram#my_histo":{
                "buckets":[
                    {
                        "key_as_string":"2018-04-01T03:00:00.000Z",
                        "key":1522551600000,
                        "doc_count":0
                    },
                    {
                        "key_as_string":"2018-04-02T03:00:00.000Z",
                        "key":1522638000000,
                        "doc_count":1
                    },
                    {
                        "key_as_string":"2018-04-03T03:00:00.000Z",
                        "key":1522724400000,
                        "doc_count":3
                    },
                    {
                        "key_as_string":"2018-04-04T03:00:00.000Z",
                        "key":1522810800000,
                        "doc_count":1
                    },
                    {
                        "key_as_string":"2018-04-05T03:00:00.000Z",
                        "key":1522897200000,
                        "doc_count":0
                    },
                    {
                        "key_as_string":"2018-04-06T03:00:00.000Z",
                        "key":1522983600000,
                        "doc_count":0
                    },
                    {
                        "key_as_string":"2018-04-07T03:00:00.000Z",
                        "key":1523070000000,
                        "doc_count":1
                    },
                    {
                        "key_as_string":"2018-04-08T03:00:00.000Z",
                        "key":1523156400000,
                        "doc_count":0
                    },
                    {
                        "key_as_string":"2018-04-09T03:00:00.000Z",
                        "key":1523242800000,
                        "doc_count":0
                    },
                    {
                        "key_as_string":"2018-04-10T03:00:00.000Z",
                        "key":1523329200000,
                        "doc_count":0
                    }
                ]
            }
        }
    }
}