Inconsistent treatment of dates without year

dates.sh

curl -XDELETE "localhost:9200/test-idx?pretty"
curl -XPUT "localhost:9200/test-idx?pretty" -d '{
    "settings": {
        "number_of_replicas": 0,
        "number_of_shards": 1
    },
    "mappings": {
        "doc": {
            "properties": {
                "event_time" : {
                    "type" : "date",
                    "format" : "MMM dd HH:mm:ss"
                }               
            }
        }
    }
}'
curl -XPUT "localhost:9200/test-idx/doc/1?pretty" -d '{"event_time":"Dec 15 14:44:24"}'
curl -XPUT "localhost:9200/test-idx/doc/2?pretty" -d '{"event_time":"Dec 15 14:44:24"}'
curl -XPOST "localhost:9200/test-idx/_refresh?pretty"
echo "========================================================================"
echo "In sort values are based on Jan 1 2000"
curl -s -XGET 127.0.0.1:9200/test-idx/doc/_search?pretty=true -d '{
    "sort": [
        {
            "event_time": {
                "order": "desc"
            }
        }
    ]
}'
echo "========================================================================"
echo "In search values are based on Jan 1 2000 for lower bound and upper bound when it's excluded"
curl -s -XGET "127.0.0.1:9200/test-idx/doc/_validate/query?pretty=true&explain=true" -d '{
    "range": {
        "event_time": {
            "lt": "Dec 15 15:00:00",
            "gt": "Dec 15 16:00:00"
        }
    }
}'
echo "========================================================================"
echo "But it based on Jan 1 1970 for upper bound if upper bound is included"
curl -s -XGET "127.0.0.1:9200/test-idx/doc/_validate/query?pretty=true&explain=true" -d '{
    "range": {
        "event_time": {
            "lte": "Dec 15 15:00:00",
            "gte": "Dec 15 16:00:00"
        }
    }
}'

output.txt

{
  "ok" : true,
  "acknowledged" : true
}
{
  "ok" : true,
  "acknowledged" : true
}
{
  "ok" : true,
  "_index" : "test-idx",
  "_type" : "doc",
  "_id" : "1",
  "_version" : 1
}
{
  "ok" : true,
  "_index" : "test-idx",
  "_type" : "doc",
  "_id" : "2",
  "_version" : 1
}
{
  "ok" : true,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  }
}
========================================================================
In sort values are based on Jan 1 2000
{
  "took" : 2,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "hits" : {
    "total" : 2,
    "max_score" : null,
    "hits" : [ {
      "_index" : "test-idx",
      "_type" : "doc",
      "_id" : "1",
      "_score" : null, "_source" : {"event_time":"Dec 15 14:44:24"},
      "sort" : [ 976891464000 ]
    }, {
      "_index" : "test-idx",
      "_type" : "doc",
      "_id" : "2",
      "_score" : null, "_source" : {"event_time":"Dec 15 14:44:24"},
      "sort" : [ 976891464000 ]
    } ]
  }
}
========================================================================
In search values are based on Jan 1 2000 for lower bound and upper bound when it's excluded
{
  "valid" : true,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "explanations" : [ {
    "index" : "test-idx",
    "valid" : true,
    "explanation" : "event_time:{976896000000 TO 976892400000}"
  } ]
}
========================================================================
But it based on Jan 1 1970 for upper bound if upper bound is included
{
  "valid" : true,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "explanations" : [ {
    "index" : "test-idx",
    "valid" : true,
    "explanation" : "event_time:[976896000000 TO 30121200999]"
  } ]
}