ElasticSearch Date Histogram Interval

Use the following format with HH instead. You're using hh which are on a 12-hours scale instead of 24-hours scale.

   "format": "dd/MM/YYYY HH:mm:ss"

UPDATE

Given your interval of 1800m, you also need to specify this offset

   "offset": "1d"

The timestamp you have highlighted in your result is not the timestamp of a document, it is the start of your first bucket.

Your first bucket goes from 31/12/2014 00:00:00 to 01/01/2015 06:00:00.

You have filtered your query to only return documents with a timestamp later than 01/01/2015 00:00:00, but since that is before 01/01/2015 06:00:00 you have documents that fall into your first bucket.

If you want to also force your buckets to start at 01/01/2015 00:00:00 then you will need to specify it as the extended_bounds.min in the histogram aggregation.

Thank you for you question Code.I solve it.I delete some code form your template code.so I did this code for work.this is very easy template for "date_histogram => date range" is ok

       var queryOptions =             {       "aggs": {         "all_hours": {             "date_histogram": {               "field": "stamp",               "interval": "1d",               "format": "dd/MM/YYYY"                         }                     }             },            "query": {       "filtered": {       "filter": {           "bool": {             "must": [               {                 "bool": {                   "must": [                     {                       "match_all": {}                     },                     {                       "range": {                         "stamp": {                           "lte": "2016-10-20",                           "gte": "2016-05-01"                         }                       }                     }                   ]                 }               }             ]           }         }      }   }  }`