diff -r c622fa18eb32 -r 145561ff51ff server/src/app/Console/Commands/IndexDocuments.php
--- a/server/src/app/Console/Commands/IndexDocuments.php	Thu Oct 20 12:56:24 2016 +0530
+++ b/server/src/app/Console/Commands/IndexDocuments.php	Thu Oct 20 11:24:45 2016 +0200
@@ -109,6 +109,13 @@
                         'creation_date' => ['type' => 'date', 'index' => 'not_analyzed'],
                         'language' => ['type' => 'string', 'index' => 'not_analyzed'],
                         'discourse_types' => ['type' => 'string', 'index' => 'not_analyzed'],
+                        'creation_years' => [
+                            'type' => 'nested',
+                            'properties' => [
+                                'year' => [ 'type' => 'short', 'index' => 'not_analyzed'],
+                                'weight' => [ 'type' => 'float', 'index' => 'not_analyzed'],
+                            ]
+                        ] ,
                         'subject' => [
                             'type' => 'nested',
                             'properties' => [
@@ -405,7 +412,7 @@
         return $date;
     }
 
-    private function processPeriod($periodStr) {
+    private function processPeriod($periodStr, $asDate=false) {
         $start = null;
         $end = null;
         foreach(explode(";", $periodStr) as $elem) {
@@ -436,18 +443,59 @@
             return null;
         }
 
-        return array_map(function($y) {
-            return \DateTime::createFromFormat("Y", "$y")->format(\DateTime::W3C);
+        return array_map(function($y) use ($asDate){
+            $date = \DateTime::createFromFormat("Y", "$y");
+            if($asDate) {
+                return $date;
+            } else {
+                return $date->format(\DateTime::W3C);
+            }
+
         }, range($start, $end));
     }
 
-    private function processDate($dateStr) {
+    private function processDate($dateStr, $asDate=false) {
         $date = $this->extractDate($dateStr);
         if(is_null($date))  {
             return null;
         } else {
-            return $date->format(\DateTime::W3C);
+            if($asDate) {
+                return $date;
+            } else {
+                return $date->format(\DateTime::W3C);
+            }
+
+        }
+    }
+
+    private function getCreationYears($doc) {
+        $created = $doc->getCreated();
+        if(is_null($created)) {
+            return [];
         }
+        $dateType = $created->getDatatypeUri();
+        $dates = null;
+
+        if($dateType === "http://purl.org/dc/terms/Period") {
+            $dates = $this->processPeriod($created->getValue(), true);
+        }
+        elseif($dateType === "http://purl.org/dc/terms/W3CDTF") {
+            $dates = $this->processDate($created->getValue(), true);
+            if(!is_null($dates)) {
+                $dates = [ $dates, ];
+            }
+        }
+        if(is_null($dates)) {
+            return [];
+        }
+        $count = count($dates);
+        return array_map(function($d) use ($count) {
+            return [
+                'year' => intval($d->format("Y")),
+                'weight' => 1/$count
+            ];
+
+        }, $dates);
     }
 
     private function getDiscourseTypes($doc) {
@@ -472,6 +520,7 @@
             'date' => (string)$doc->getModified(),
             'location' => $this->getLocation($doc),
             'creation_date' => $this->getCreationDate($doc),
+            'creation_years' => $this->getCreationYears($doc),
             'language' => $doc->getLanguagesValue(),
             'discourse_types' => $this->getDiscourseTypes($doc),
             'geonames_hierarchy' => $this->getGeonamesHierarchy($doc),