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# Date Histogram Aggregation
> More info about histogram aggregation is in the [official elasticsearch docs][1]
A multi-bucket aggregation similar to the histogram except it can only be applied on date values.
Example of expressions for interval: `year`, `quarter`, `month`, `week`, `day`, `hour`, `minute`, `second`
## Simple example
```JSON
{
"aggregations": {
"articles_over_time" : {
"date_histogram" : {
"field" : "date",
"interval" : "month"
}
}
}
}
```
And now the query via DSL:
```php
$dateHistogramAggregation = new DateHistogramAggregation('articles_over_time', 'date', 'month');
$search = new Search();
$search->addAggregation($dateHistogramAggregation);
$queryArray = $search->toArray();
```
## Adding parameters example
Additional parameters can be added to the aggregation. In the following example we will demonstrate how
to provide a custom format to the results of the query:
```JSON
{
"aggregations": {
"articles_over_time" : {
"date_histogram" : {
"field" : "date",
"interval" : "1M",
"format" : "yyyy-MM-dd"
}
}
}
}
```
And now the query via DSL:
```php
$dateHistogramAggregation = new DateHistogramAggregation('articles_over_time', 'date', 'month');
$dateHistogramAggregation->addParameter('format', 'yyyy-MM-dd');
$search = new Search();
$search->addAggregation($dateHistogramAggregation);
$queryArray = $search->toArray();
```
[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html
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