Merge pull request #244 from blesenechal/fix-date-filter

Fix api-platform/core issue #1326 (DateFilter before/after filters on before or equals/after or equals)

Author: Simperfit

core/filters.md

@@ -88,10 +88,12 @@ Previous URLs will return all offers for the product having the following IRI as
 
 The date filter allows to filter a collection by date intervals.
 
-Syntax: `?property[<after|before>]=value`
+Syntax: `?property[<after|before|strictly_after|strictly_before>]=value`
 
 The value can take any date format supported by the [`\DateTime` constructor](http://php.net/manual/en/datetime.construct.php).
 
+The `after` and `before` filters will filter including the value whereas `strictly_after` and `strictly_before` will filter excluding the value.
+
 As others filters, the date filter must be explicitly enabled:
 
 ```yaml