diff --git a/app/Http/Controllers/Apis/Protected/Summit/Factories/SummitValidationRulesFactory.php b/app/Http/Controllers/Apis/Protected/Summit/Factories/SummitValidationRulesFactory.php
index 4ac04a5d..528fe629 100644
--- a/app/Http/Controllers/Apis/Protected/Summit/Factories/SummitValidationRulesFactory.php
+++ b/app/Http/Controllers/Apis/Protected/Summit/Factories/SummitValidationRulesFactory.php
@@ -23,17 +23,17 @@ final class SummitValidationRulesFactory
             return [
                 'name'                      => 'sometimes|string|max:50',
                 'start_date'                => 'sometimes|date_format:U',
-                'end_date'                  => 'required_with:start_date|date_format:U|after:start_date',
-                'submission_begin_date'     => 'sometimes|date_format:U',
-                'submission_end_date'       => 'required_with:submission_begin_date|date_format:U|after:submission_begin_date',
-                'voting_begin_date'         => 'sometimes|date_format:U',
-                'voting_end_date'           => 'required_with:voting_begin_date|date_format:U|after:voting_begin_date',
-                'selection_begin_date'      => 'sometimes|date_format:U',
-                'selection_end_date'        => 'required_with:selection_begin_date|date_format:U|after:selection_begin_date',
-                'registration_begin_date'   => 'sometimes|date_format:U',
-                'registration_end_date'     => 'required_with:registration_begin_date|date_format:U|after:registration_begin_date',
-                'start_showing_venues_date' => 'sometimes|date_format:U|before:start_date',
-                'schedule_start_date'       => 'sometimes|date_format:U',
+                'end_date'                  => 'required_with:start_date|date_format:U|after_or_equal:start_date',
+                'submission_begin_date'     => 'nullable|date_format:U',
+                'submission_end_date'       => 'nullable|required_with:submission_begin_date|date_format:U|after_or_equal:submission_begin_date',
+                'voting_begin_date'         => 'nullable|date_format:U',
+                'voting_end_date'           => 'nullable|required_with:voting_begin_date|date_format:U|after_or_equal:voting_begin_date',
+                'selection_begin_date'      => 'nullable|date_format:U',
+                'selection_end_date'        => 'nullable|required_with:selection_begin_date|date_format:U|after_or_equal:selection_begin_date',
+                'registration_begin_date'   => 'nullable|date_format:U',
+                'registration_end_date'     => 'nullable|required_with:registration_begin_date|date_format:U|after_or_equal:registration_begin_date',
+                'start_showing_venues_date' => 'nullable|date_format:U|before_or_equal:start_date',
+                'schedule_start_date'       => 'nullable|date_format:U|after_or_equal:start_date|before_or_equal:end_date',
                 'active'                    => 'sometimes|boolean',
                 'dates_label'               => 'sometimes|string',
                 'time_zone_id'              => 'sometimes|timezone',
@@ -42,31 +42,31 @@ final class SummitValidationRulesFactory
                 'calendar_sync_name'        => 'sometimes|string|max:255',
                 'calendar_sync_desc'        => 'sometimes|string',
                 'link'                      => 'sometimes|url',
-                'registration_link'         => 'sometimes|url',
-                'max_submission_allowed_per_user'  => 'sometimes|integer|min:1',
-                'secondary_registration_link' => 'sometimes|url',
-                'secondary_registration_label' => 'sometimes|string',
+                'registration_link'               => 'sometimes|url',
+                'max_submission_allowed_per_user' => 'sometimes|integer|min:1',
+                'secondary_registration_link'     => 'sometimes|url',
+                'secondary_registration_label'    => 'sometimes|string',
             ];
         }
 
         return [
             'name'                      => 'required|string|max:50',
             'start_date'                => 'required|date_format:U',
-            'end_date'                  => 'required_with:start_date|date_format:U|after:start_date',
-            'submission_begin_date'     => 'sometimes|date_format:U',
-            'submission_end_date'       => 'required_with:submission_begin_date|date_format:U|after:submission_begin_date',
-            'voting_begin_date'         => 'sometimes|date_format:U',
-            'voting_end_date'           => 'required_with:voting_begin_date|date_format:U|after:voting_begin_date',
-            'selection_begin_date'      => 'sometimes|date_format:U',
-            'selection_end_date'        => 'required_with:selection_begin_date|date_format:U|after:selection_begin_date',
-            'registration_begin_date'   => 'sometimes|date_format:U',
-            'registration_end_date'     => 'required_with:registration_begin_date|date_format:U|after:registration_begin_date',
-            'start_showing_venues_date' => 'sometimes|date_format:U|before:start_date',
-            'schedule_start_date'       => 'sometimes|date_format:U',
+            'end_date'                  => 'required_with:start_date|date_format:U|after_or_equal:start_date',
+            'submission_begin_date'     => 'nullable|date_format:U',
+            'submission_end_date'       => 'nullable|required_with:submission_begin_date|date_format:U|after_or_equal:submission_begin_date',
+            'voting_begin_date'         => 'nullable|date_format:U',
+            'voting_end_date'           => 'nullable|required_with:voting_begin_date|date_format:U|after_or_equal:voting_begin_date',
+            'selection_begin_date'      => 'nullable|date_format:U',
+            'selection_end_date'        => 'nullable|required_with:selection_begin_date|date_format:U|after_or_equal:selection_begin_date',
+            'registration_begin_date'   => 'nullable|date_format:U',
+            'registration_end_date'     => 'nullable|required_with:registration_begin_date|date_format:U|after_or_equal:registration_begin_date',
+            'start_showing_venues_date' => 'nullable|date_format:U|before_or_equal:start_date',
+            'schedule_start_date'       => 'nullable|date_format:U|after_or_equal:start_date|before_or_equal:end_date',
             'active'                    => 'sometimes|boolean',
             'dates_label'               => 'sometimes|string',
             'time_zone_id'              => 'required|timezone',
-            'external_summit_id'        => 'sometimes|string',
+            'external_summit_id'        => 'nullable|string',
             'available_on_api'          => 'sometimes|boolean',
             'calendar_sync_name'        => 'sometimes|string|max:255',
             'calendar_sync_desc'        => 'sometimes|string',
diff --git a/app/Models/Foundation/Summit/Factories/SummitFactory.php b/app/Models/Foundation/Summit/Factories/SummitFactory.php
index f9d07bde..5db79219 100644
--- a/app/Models/Foundation/Summit/Factories/SummitFactory.php
+++ b/app/Models/Foundation/Summit/Factories/SummitFactory.php
@@ -65,87 +65,122 @@ final class SummitFactory
             $summit->setCalendarSyncDesc(trim($data['calendar_sync_desc']));
         }
 
-        if(isset($data['start_date']) && isset($data['end_date'])) {
-            $start_datetime = intval($data['start_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
-            $end_datetime = intval($data['end_date']);
-            $end_datetime = new \DateTime("@$end_datetime");
-            $end_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('start_date', $data) && array_key_exists('end_date', $data)) {
+            if (isset($data['start_date']) && isset($data['end_date'])) {
+                $start_datetime = intval($data['start_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
+                $end_datetime = intval($data['end_date']);
+                $end_datetime = new \DateTime("@$end_datetime");
+                $end_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setBeginDate($start_datetime);
-            $summit->setEndDate($end_datetime);
+                // set local time from UTC
+                $summit->setBeginDate($start_datetime);
+                $summit->setEndDate($end_datetime);
+            }
+            else{
+                $summit->clearBeginEndDates();
+            }
         }
 
-        if(isset($data['submission_begin_date']) && isset($data['submission_end_date'])) {
-            $start_datetime = intval($data['submission_begin_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
-            $end_datetime = intval($data['submission_end_date']);
-            $end_datetime = new \DateTime("@$end_datetime");
-            $end_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('submission_begin_date', $data) && array_key_exists('submission_end_date', $data)) {
+            if (isset($data['submission_begin_date']) && isset($data['submission_end_date'])) {
+                $start_datetime = intval($data['submission_begin_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
+                $end_datetime = intval($data['submission_end_date']);
+                $end_datetime = new \DateTime("@$end_datetime");
+                $end_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setSubmissionBeginDate($start_datetime);
-            $summit->setSubmissionEndDate($end_datetime);
+                // set local time from UTC
+                $summit->setSubmissionBeginDate($start_datetime);
+                $summit->setSubmissionEndDate($end_datetime);
+            }
+            else{
+                $summit->clearSubmissionDates();
+            }
         }
 
-        if(isset($data['voting_begin_date']) && isset($data['voting_end_date'])) {
-            $start_datetime = intval($data['voting_begin_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
-            $end_datetime = intval($data['voting_end_date']);
-            $end_datetime = new \DateTime("@$end_datetime");
-            $end_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('voting_begin_date', $data) && array_key_exists('voting_end_date', $data)) {
+            if (isset($data['voting_begin_date']) && isset($data['voting_end_date'])) {
+                $start_datetime = intval($data['voting_begin_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
+                $end_datetime = intval($data['voting_end_date']);
+                $end_datetime = new \DateTime("@$end_datetime");
+                $end_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setVotingBeginDate($start_datetime);
-            $summit->setVotingEndDate($end_datetime);
+                // set local time from UTC
+                $summit->setVotingBeginDate($start_datetime);
+                $summit->setVotingEndDate($end_datetime);
+            }
+            else{
+                $summit->clearVotingDates();
+            }
         }
 
-        if(isset($data['selection_begin_date']) && isset($data['selection_end_date'])) {
-            $start_datetime = intval($data['selection_begin_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
-            $end_datetime = intval($data['selection_end_date']);
-            $end_datetime = new \DateTime("@$end_datetime");
-            $end_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('selection_begin_date', $data) && array_key_exists('selection_end_date', $data)) {
+            if (isset($data['selection_begin_date']) && isset($data['selection_end_date'])) {
+                $start_datetime = intval($data['selection_begin_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
+                $end_datetime = intval($data['selection_end_date']);
+                $end_datetime = new \DateTime("@$end_datetime");
+                $end_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setSelectionBeginDate($start_datetime);
-            $summit->setSelectionEndDate($end_datetime);
+                // set local time from UTC
+                $summit->setSelectionBeginDate($start_datetime);
+                $summit->setSelectionEndDate($end_datetime);
+            }
+            else{
+                $summit->clearSelectionDates();
+            }
         }
 
-        if(isset($data['registration_begin_date']) && isset($data['registration_end_date'])) {
-            $start_datetime = intval($data['registration_begin_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
-            $end_datetime = intval($data['registration_end_date']);
-            $end_datetime = new \DateTime("@$end_datetime");
-            $end_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('registration_begin_date', $data) && array_key_exists('registration_end_date', $data)) {
+            if (isset($data['registration_begin_date']) && isset($data['registration_end_date'])) {
+                $start_datetime = intval($data['registration_begin_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
+                $end_datetime = intval($data['registration_end_date']);
+                $end_datetime = new \DateTime("@$end_datetime");
+                $end_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setRegistrationBeginDate($start_datetime);
-            $summit->setRegistrationEndDate($end_datetime);
+                // set local time from UTC
+                $summit->setRegistrationBeginDate($start_datetime);
+                $summit->setRegistrationEndDate($end_datetime);
+            }
+            else{
+                $summit->clearRegistrationDates();
+            }
         }
 
-        if(isset($data['start_showing_venues_date'])) {
-            $start_datetime = intval($data['start_showing_venues_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('start_showing_venues_date', $data)){
+            if (isset($data['start_showing_venues_date'])) {
+                $start_datetime = intval($data['start_showing_venues_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setStartShowingVenuesDate($start_datetime);
+                // set local time from UTC
+                $summit->setStartShowingVenuesDate($start_datetime);
+            }
+            else{
+                $summit->clearStartShowingVenuesDate();
+            }
         }
 
-        if(isset($data['schedule_start_date'])) {
-            $start_datetime = intval($data['schedule_start_date']);
-            $start_datetime = new \DateTime("@$start_datetime");
-            $start_datetime->setTimezone($summit->getTimeZone());
+        if(array_key_exists('schedule_start_date', $data)) {
+            if (isset($data['schedule_start_date'])) {
+                $start_datetime = intval($data['schedule_start_date']);
+                $start_datetime = new \DateTime("@$start_datetime");
+                $start_datetime->setTimezone($summit->getTimeZone());
 
-            // set local time from UTC
-            $summit->setScheduleDefaultStartDate($start_datetime);
+                // set local time from UTC
+                $summit->setScheduleDefaultStartDate($start_datetime);
+            }
+            else{
+                $summit->clearScheduleDefaultStartDate();
+            }
         }
 
         if(isset($data['link']) ){
diff --git a/app/Models/Foundation/Summit/Summit.php b/app/Models/Foundation/Summit/Summit.php
index 10a00d16..69e683db 100644
--- a/app/Models/Foundation/Summit/Summit.php
+++ b/app/Models/Foundation/Summit/Summit.php
@@ -390,6 +390,10 @@ class Summit extends SilverstripeBaseModel
         $this->schedule_default_start_date = $this->convertDateFromTimeZone2UTC($schedule_default_start_date);
     }
 
+    public function clearScheduleDefaultStartDate(){
+        $this->schedule_default_start_date = null;
+    }
+
     /**
      * @return mixed
      */
@@ -406,6 +410,14 @@ class Summit extends SilverstripeBaseModel
        $this->begin_date = $this->convertDateFromTimeZone2UTC($begin_date);
     }
 
+    /**
+     * @return $this
+     */
+    public function clearBeginEndDates(){
+        $this->begin_date = $this->end_date = null;
+        return $this;
+    }
+
     /**
      * @return \DateTime
      */
@@ -454,6 +466,10 @@ class Summit extends SilverstripeBaseModel
         $this->start_showing_venues_date = $this->convertDateFromTimeZone2UTC($start_showing_venues_date);
     }
 
+    public function clearStartShowingVenuesDate(){
+        $this->start_showing_venues_date = null;
+    }
+
     /**
      * @return boolean
      */
@@ -1393,6 +1409,14 @@ SQL;
         $this->submission_begin_date = $this->convertDateFromTimeZone2UTC($submission_begin_date);
     }
 
+    /**
+     * @return $this
+     */
+    public function clearSubmissionDates(){
+        $this->submission_begin_date =  $this->submission_end_date = null;
+        return $this;
+    }
+
     /**
      * @return DateTime
      */
@@ -1423,6 +1447,14 @@ SQL;
         $this->voting_begin_date = $this->convertDateFromTimeZone2UTC($voting_begin_date);
     }
 
+    /**
+     * @return $this
+     */
+    public function clearVotingDates(){
+        $this->voting_begin_date = $this->voting_end_date = null;
+        return $this;
+    }
+
     /**
      * @return DateTime
      */
@@ -1453,6 +1485,14 @@ SQL;
         $this->selection_begin_date = $this->convertDateFromTimeZone2UTC($selection_begin_date);
     }
 
+    /**
+     * @return $this
+     */
+    public function clearSelectionDates(){
+        $this->selection_begin_date =  $this->selection_end_date = null;
+        return $this;
+    }
+
     /**
      * @return DateTime
      */
@@ -1483,6 +1523,14 @@ SQL;
         $this->registration_begin_date = $this->convertDateFromTimeZone2UTC($registration_begin_date);
     }
 
+    /**
+     * @return $this
+     */
+    public function clearRegistrationDates(){
+        $this->registration_begin_date = $this->registration_end_date = null;
+        return $this;
+    }
+
     /**
      * @return DateTime
      */
diff --git a/tests/OAuth2SummitApiTest.php b/tests/OAuth2SummitApiTest.php
index a4845a0a..6a3d3ff8 100644
--- a/tests/OAuth2SummitApiTest.php
+++ b/tests/OAuth2SummitApiTest.php
@@ -127,7 +127,7 @@ final class OAuth2SummitApiTest extends ProtectedApiTest
             'name'         => 'Vancouver, BC',
             'start_date'   => 1522853212,
             'end_date'     => 1542853212,
-            'time_zone_id' => 'America/Argentina/Buenos_Aires'
+            'time_zone_id' => 'America/Argentina/Buenos_Aires',
         ];
 
         $headers = [
@@ -158,7 +158,9 @@ final class OAuth2SummitApiTest extends ProtectedApiTest
             'name'         => $name,
             'start_date'   => 1522853212,
             'end_date'     => 1542853212,
-            'time_zone_id' => 'America/Argentina/Buenos_Aires'
+            'time_zone_id' => 'America/Argentina/Buenos_Aires',
+            'submission_begin_date' => null,
+            'submission_end_date' => null,
         ];
 
         $headers = [