diff -u b/src/Plugin/facets/facet_source/SearchApiBaseFacetSource.php b/src/Plugin/facets/facet_source/SearchApiBaseFacetSource.php
--- b/src/Plugin/facets/facet_source/SearchApiBaseFacetSource.php
+++ b/src/Plugin/facets/facet_source/SearchApiBaseFacetSource.php
@@ -128,16 +128,15 @@
     $query_types = [];
     // @todo Make this flexible for each data type in Search API.
     switch ($data_type_plugin_id) {
+      case 'date':
+        $query_types['date'] = 'search_api_date';
       case 'boolean':
       case 'decimal':
       case 'integer':
+        $query_types['numeric'] = 'search_api_granular';
       case 'string':
       case 'text':
         $query_types['string'] = 'search_api_string';
-        break;
-      case 'date':
-        $query_types['date'] = 'search_api_date';
-        break;
     }
 
     // Find out if the backend implemented the Interface to retrieve specific
diff -u b/src/Plugin/facets/query_type/SearchApiDate.php b/src/Plugin/facets/query_type/SearchApiDate.php
--- b/src/Plugin/facets/query_type/SearchApiDate.php
+++ b/src/Plugin/facets/query_type/SearchApiDate.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\facets\Plugin\facets\query_type;
 
-use Drupal\facets\QueryType\QueryTypePluginBase;
-use Drupal\facets\Result\Result;
+use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\facets\QueryType\QueryTypeRangeBase;
 
 /**
  * Support for date facets within the Search API scope.
@@ -21,8 +21,11 @@
  *   label = @Translation("Date"),
  * )
  */
-class SearchApiDate extends SearchApiGranular {
+class SearchApiDate extends QueryTypeRangeBase {
 
+  /**
+   * Granularity constants for grouping results.
+   */
   const FACETAPI_DATE_YEAR = 6;
   const FACETAPI_DATE_MONTH = 5;
   const FACETAPI_DATE_DAY = 4;
@@ -30,87 +33,301 @@
   const FACETAPI_DATE_MINUTE = 2;
   const FACETAPI_DATE_SECOND = 1;
 
+  /**
+   * {@inheritdoc}
+   */
   public function calculateRange($value) {
-    $dateTime = new \DateTime();
+    if ($this->getDisplayRelative()) {
+      return $this->calculateRangeRelative($value);
+    }
+    else {
+      return $this->calculateRangeAbsolute($value);
+    }
+  }
+
+  protected function calculateRangeAbsolute($value) {
+    $dateTime = new DrupalDateTime();
     switch ($this->getGranularity()) {
       case static::FACETAPI_DATE_YEAR:
-        $startDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '1-1T00:00:00');
-        $stopDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '12-3123:59:59');
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '1-1T00:00:00');
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '12-3123:59:59');
         break;
       case static::FACETAPI_DATE_MONTH:
-        $startDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '-1T00:00:00');
-        $stopDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '-31T23:59:59');
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '-1T00:00:00');
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '-31T23:59:59');
         break;
       case static::FACETAPI_DATE_DAY:
-        $startDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . 'T00:00:00');
-        $stopDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . 'T23:59:59');
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . 'T00:00:00');
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . 'T23:59:59');
         break;
       case static::FACETAPI_DATE_HOUR:
-        $startDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '00:00');
-        $stopDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . '59:59');
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '00:00');
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '59:59');
         break;
       case static::FACETAPI_DATE_MINUTE:
-        $startDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':00');
-        $stopDate = \DateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':59');
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':00');
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':59');
         break;
       case static::FACETAPI_DATE_SECOND:
-        $value_start = $value;
-        $value_stop = $value;
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value);
+        $stopDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value);
         break;
     }
-    $value_start = $startDate->format('U');
-    $value_stop = $stopDate->format('U');
 
     return [
-      'start' => $value_start,
-      'stop' => $value_stop,
+      'start' => $startDate->format('U'),
+      'stop' => $stopDate->format('U'),
     ];
   }
 
+  protected function calculateRangeRelative($value) {
+    $dateTime = new DrupalDateTime();
+    switch ($this->getGranularity()) {
+      case static::FACETAPI_DATE_YEAR:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . '-1T00:00:00');
+        $stopDate = clone $startDate;
+        $stopDate->add(new \DateInterval('P1Y'));
+        $stopDate->sub(new \DateInterval('PT1S'));
+        break;
+      case static::FACETAPI_DATE_MONTH:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . 'T00:00:00');
+        $stopDate = clone $startDate;
+        $stopDate->add(new \DateInterval('P1M'));
+        $stopDate->sub(new \DateInterval('PT1S'));
+        break;
+      case static::FACETAPI_DATE_DAY:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':00:00');
+        $stopDate = clone $startDate;
+        $stopDate->add(new \DateInterval('P1D'));
+        $stopDate->sub(new \DateInterval('PT1S'));
+        break;
+      case static::FACETAPI_DATE_HOUR:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value . ':00');
+        $stopDate = clone $startDate;
+        $stopDate->add(new \DateInterval('PT1H'));
+        $stopDate->sub(new \DateInterval('PT1S'));
+        break;
+      case static::FACETAPI_DATE_MINUTE:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value);
+        $stopDate = clone $startDate;
+        $stopDate->add(new \DateInterval('PT1M'));
+        $stopDate->sub(new \DateInterval('PT1S'));
+        break;
+      case static::FACETAPI_DATE_SECOND:
+        $startDate = $dateTime::createFromFormat('Y-m-d\TH:i:s', $value);
+        $stopDate = clone $startDate;
+        break;
+    }
+
+    return [
+      'start' => $startDate->format('U'),
+      'stop' => $stopDate->format('U'),
+    ];
+  }
+
+
+  public function calculateResultFilter($value) {
+    if ($this->getDisplayRelative()) {
+      return $this->calculateResultFilterRelative($value);
+    }
+    else {
+      return $this->calculateResultFilterAbsolute($value);
+    }
+  }
+
   /**
-   * {@inherit}
-   *
-   * @todo make display format configurable.
+   * {@inheritdoc}
    */
-  public function calculateResultFilter($value) {
-    $date = new \DateTime();
+  public function calculateResultFilterAbsolute($value) {
+    $date = new DrupalDateTime();
     $date->setTimestamp($value);
-
+    $date_display = $this->getDateFormat();
     switch ($this->getGranularity()) {
       case static::FACETAPI_DATE_YEAR:
         $format = 'Y';
-        return [
-          'display' => $date->format('Y'),
-          'raw' => $date->format('Y'),
-        ];
+        $raw = $date->format('Y');
+        break;
       case static::FACETAPI_DATE_MONTH:
-        return [
-          'display' => $date->format('F Y'),
-          'raw' => $date->format('Y-m'),
-        ];
+        $format = 'F Y';
+        $raw = $date->format('Y-m');
+        break;
       case static::FACETAPI_DATE_DAY:
-        return [
-          'display' => $date->format('d F Y'),
-          'raw' => $date->format('Y-m-d'),
-        ];
+        $format = 'd F Y';
+        $raw = $date->format('Y-m-d');
+        break;
       case static::FACETAPI_DATE_HOUR:
-        return [
-          'display' => $date->format('d/m/Y H\h'),
-          'raw' => $date->format('Y-m-d\TH'),
-        ];
+        $format = 'd/m/Y H\h';
+        $raw = $date->format('Y-m-d\TH');
+        break;
+      case static::FACETAPI_DATE_MINUTE:
+        $format = 'd/m/Y H:i';
+        $raw = $date->format('Y-m-d\TH:i');
+        break;
+      case static::FACETAPI_DATE_SECOND:
+        $format = 'd/m/Y H:i:s';
+        $raw = $date->format('Y-m-d\TH:i:s');
+        break;
+    }
+    $format = $date_display ? $date_display : $format;
+    return [
+      'display' => $date->format($format),
+      'raw' => $raw,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function calculateResultFilterRelative($value) {
+    $date = new DrupalDateTime();
+    $date->setTimestamp($value);
+    $now = new DrupalDateTime();
+    $now->setTimestamp(REQUEST_TIME);
+    $interval = $date->diff($now);
+    $future = $date > $now;
+
+    switch ($this->getGranularity()) {
+      case static::FACETAPI_DATE_YEAR:
+        $rounded = new \DateInterval('P' . $interval->y . 'Y');
+        if ($future) {
+          $display = $interval->y ? $this->formatPlural($interval->y, '1 year hence', '@count years hence') : $this->t('In the next year');
+          $now->add($rounded);
+        }
+        else {
+          $display = $interval->y ? $this->formatPlural($interval->y, '1 year ago', '@count years ago') : $this->t('In the last year');
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('P1Y'));
+        }
+        $raw = $now->format('Y-m');
+        break;
+      case static::FACETAPI_DATE_MONTH:
+        $rounded = new \DateInterval('P' . $interval->y . 'Y' . $interval->m . 'M');
+        $display = $interval->y ? $this->formatPlural($interval->y, '1 year', '@count years') . ' ' : '';
+        if ($future) {
+          $display .= $interval->m ?
+            $this->formatPlural($interval->m, '1 month hence', '@count months hence') :
+            (empty($display) ? $this->t('In the next month') : $this->t('0 months hence'));
+          $now->add($rounded);
+        }
+        else {
+          $display .= $interval->m ?
+            $this->formatPlural($interval->m, '1 month ago', '@count months ago') :
+            (empty($display) ? $this->t('In the last month') : $this->t('0 months ago'));
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('P1M'));
+        }
+        $raw = $now->format('Y-m-d');
+        break;
+      case static::FACETAPI_DATE_DAY:
+        $rounded = new \DateInterval('P' . $interval->y . 'Y' . $interval->m . 'M' . $interval->d . 'D');
+        $display = $interval->y ? $this->formatPlural($interval->y, '1 year', '@count years') . ' ' : '';
+        $display .= $interval->m ? $this->formatPlural($interval->m, '1 month', '@count months') . ' ' : '';
+        if ($future) {
+          $display .= $interval->d ?
+            $this->formatPlural($interval->d, '1 day hence', '@count days hence') :
+            (empty($display) ? $this->t('In the next day') : $this->t('0 days hence'));
+          $now->add($rounded);
+        }
+        else {
+          $display .= $interval->d ?
+            $this->formatPlural($interval->d, '1 day ago', '@count days ago') :
+            (empty($display) ? $this->t('In the last day') : $this->t('0 days ago'));
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('P1D'));
+        }
+        $raw = $now->format('Y-m-d\TH');
+        break;
+      case static::FACETAPI_DATE_HOUR:
+        $rounded = new \DateInterval('P' . $interval->y . 'Y' . $interval->m . 'M' . $interval->d . 'DT' . $interval->h . 'H');
+        $display = $interval->y ? $this->formatPlural($interval->y, '1 year', '@count years') . ' ' : '';
+        $display .= $interval->m ? $this->formatPlural($interval->m, '1 month', '@count months') . ' ' : '';
+        $display .= $interval->d ? $this->formatPlural($interval->d, '1 day', '@count days') . ' ' : '';
+        if ($future) {
+          $display .= $interval->h ?
+            $this->formatPlural($interval->h, '1 hour hence', '@count hours hence') :
+            (empty($display) ? $this->t('In the next hour') : $this->t('0 hours hence'));
+          $now->add($rounded);
+        }
+        else {
+          $display .= $interval->h ?
+            $this->formatPlural($interval->h, '1 hour ago', '@count hours ago') :
+            (empty($display) ? $this->t('In the last hour') : $this->t('0 hours ago'));
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('PT1H'));
+        }
+        $raw = $now->format('Y-m-d\TH:i');
+        break;
       case static::FACETAPI_DATE_MINUTE:
-        return [
-          'display' => $date->format('d/m/Y H:i'),
-          'raw' => $date->format('Y-m-d\TH:i'),
-        ];
+        $rounded = new \DateInterval('P' . $interval->y . 'Y' . $interval->m . 'M' . $interval->d . 'DT' . $interval->h . 'H' . $interval->i);
+        $display = $interval->y ? $this->formatPlural($interval->y, '1 year', '@count years') . ' ' : '';
+        $display .= $interval->m ? $this->formatPlural($interval->m, '1 month', '@count months') . ' ' : '';
+        $display .= $interval->d ? $this->formatPlural($interval->d, '1 day', '@count days') . ' ' : '';
+        $display .= $interval->h ? $this->formatPlural($interval->h, '1 hour', '@count hours') . ' ' : '';
+        if ($future) {
+          $display .= $interval->i ?
+            $this->formatPlural($interval->i, '1 minute hence', '@count minutes hence') :
+            (empty($display) ? $this->t('In the next minute') : $this->t('0 minutes hence'));
+          $now->add($rounded);
+        }
+        else {
+          $display .= $interval->i ?
+            $this->formatPlural($interval->i, '1 minute ago', '@count minutes ago') :
+            (empty($display) ? $this->t('In the last minute') : $this->t('0 minutes ago'));
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('PT1M'));
+        }
+        $raw = $date->format('Y-m-d\TH:i:s');
         break;
       case static::FACETAPI_DATE_SECOND:
-        return [
-          'display' => $date->format('d/m/Y H:i:s'),
-          'raw' => $date->format('Y-m-d\TH:i:s'),
-        ];
+        $rounded = new \DateInterval('P' . $interval->y . 'Y' . $interval->m . 'M' . $interval->d . 'DT' . $interval->h . 'H' . $interval->i . $interval->s . 'S');
+        $display = $interval->y ? $this->formatPlural($interval->y, '1 year', '@count years') . ' ' : '';
+        $display .= $interval->m ? $this->formatPlural($interval->m, '1 month', '@count months') . ' ' : '';
+        $display .= $interval->d ? $this->formatPlural($interval->d, '1 day', '@count days') . ' ' : '';
+        $display .= $interval->h ? $this->formatPlural($interval->h, '1 hour', '@count hours') . ' ' : '';
+        $display .= $interval->i ? $this->formatPlural($interval->i, '1 minute', '@count minutes') . ' ' : '';
+        if ($future) {
+          $display .= $interval->s ?
+            $this->formatPlural($interval->s, '1 second hence', '@count seconds hence') :
+            (empty($display) ? $this->t('In the next second') : $this->t('0 secondss hence'));
+          $now->add($rounded);
+        }
+        else {
+          $display .= $interval->s ?
+            $this->formatPlural($interval->s, '1 second ago', '@count seconds ago') :
+            (empty($display) ? $this->t('In the last second') : $this->t('0 seconds ago'));
+          $now->sub($rounded);
+          $now->sub(new \DateInterval('PT1S'));
+        }
+        $raw = $date->format('Y-m-d\TH:i:s');
         break;
     }
+    return [
+      'display' => $display,
+      'raw' => $raw,
+    ];
+  }
+
+  /**
+   * Retrieve configuration: Granularity to use.
+   *
+   * Default behaviour an integer for the steps that the facet works in.
+   */
+  protected function getGranularity() {
+    return $this->facet->getWidgetInstance()->getConfiguration()['granularity'];
+  }
+
+  /**
+   * Retrieve configuration: If the date should be displayed relatively.
+   */
+  protected function getDisplayRelative() {
+    return $this->facet->getWidgetInstance()->getConfiguration()['display_relative'];
+  }
+
+  /**
+   * Retrieve configuration: Date display format.
+   */
+  protected function getDateFormat() {
+    return $this->facet->getWidgetInstance()->getConfiguration()['date_display'];
   }
 
 }
diff -u b/src/Plugin/facets/widget/DateBasicWidget.php b/src/Plugin/facets/widget/DateBasicWidget.php
--- b/src/Plugin/facets/widget/DateBasicWidget.php
+++ b/src/Plugin/facets/widget/DateBasicWidget.php
@@ -42,7 +42,11 @@
    */
   public function defaultConfiguration() {
     $configuration = parent::defaultConfiguration();
+    $configuration['display_relative'] = FALSE;
     $configuration['granularity'] = SearchApiDate::FACETAPI_DATE_MONTH;
+    $configuration['date_display'] = '';
+    $configuration['relative_granularity'] = 1;
+    $configuration['relative_text'] = TRUE;
   }
 
   /**
@@ -53,12 +57,31 @@
 
     $form += parent::buildConfigurationForm($form, $form_state, $facet);
 
+    $form['display_relative'] = [
+      '#type' => 'radios',
+      '#title' => $this->t('Date display'),
+      '#default_value' => $configuration['display_relative'],
+      '#options' => [
+        FALSE => $this->t('Actual date with granularity'),
+        TRUE => $this->t('Relative date'),
+      ],
+    ];
+
     $form['granularity'] = [
       '#type' => 'radios',
       '#title' => $this->t('Granularity'),
       '#default_value' => $configuration['granularity'],
       '#options' => $this->granularityOptions(),
     ];
+    $form['date_display'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Date format'),
+      '#default_value' => $configuration['date_display'],
+      '#description' => $this->t('Override default date format used for the displayed filter format. See the <a href="http://php.net/manual/function.date.php">PHP manual</a> for available options.'),
+      '#states' => [
+        'visible' => [':input[name="widget_config[display_relative]"]' => ['value' => 0]],
+      ],
+    ];
 
     return $form;
   }
only in patch2:
unchanged:
--- /dev/null
+++ b/src/Plugin/facets/widget/NumericGranularWidget.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Drupal\facets\Plugin\facets\widget;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\facets\FacetInterface;
+use Drupal\facets\Result\Result;
+use Drupal\facets\Widget\WidgetPluginBase;
+use Drupal\facets\Plugin\facets\query_type\SearchApiDate;
+
+
+/**
+ * Basic granular widget.
+ *
+ * @FacetsWidget(
+ *   id = "numericgranular",
+ *   label = @Translation("Granular numeric list"),
+ *   description = @Translation("List of numbers grouped in steps."),
+ * )
+ */
+class NumericGranularWidget extends LinksWidget {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    $configuration = parent::defaultConfiguration();
+    $configuration['granularity'] = 0;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state, FacetInterface $facet) {
+    $configuration = $this->getConfiguration();
+
+    $form += parent::buildConfigurationForm($form, $form_state, $facet);
+
+    $form['granularity'] = [
+      '#type' => 'number',
+      '#title' => $this->t('Granularity'),
+      '#default_value' => $configuration['granularity'],
+      '#description' => $this->t('The numeric size of the steps to group the result facets in.'),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getQueryType($query_types) {
+    return $query_types['numeric'];
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/tests/src/Unit/Plugin/query_type/SearchApiDateTest.php
@@ -0,0 +1,279 @@
+<?php
+
+namespace Drupal\Tests\facets\Unit\Plugin\query_type;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\facets\Entity\Facet;
+use Drupal\facets\Plugin\facets\query_type\SearchApiDate;
+use Drupal\search_api\Plugin\views\query\SearchApiQuery;
+
+/**
+ * Unit test for date query type.
+ *
+ * @group facets
+ */
+class SearchApiDateTest extends KernelTestBase {
+
+  public function setUp() {
+    parent::setUp();
+
+    // This is the default set by Drupal as well, but to be explicit
+    // The raw value is the UTC, the displayed value is calculated
+    // by the PHP timezone - presently.
+    date_default_timezone_set('Australia/Sydney');
+  }
+
+  /**
+   * Tests string query type without executing the query with an "AND" operator.
+   *
+   * @dataProvider resultsProvider
+   */
+  public function testQueryTypeAnd($granularity, $original_results, $grouped_results) {
+    $query = new SearchApiQuery([], 'search_api_query', []);
+    $facetReflection = new \ReflectionClass ('Drupal\facets\Entity\Facet');
+    $facet = new Facet(
+      ['query_operator' => 'AND'],
+      'facets_facet'
+    );
+    $widget = $this->getMockBuilder('Drupal\facets\Widget\WidgetPluginInterface')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $widget->method('getConfiguration')->will($this->returnValue(
+      [
+        'granularity' => $granularity,
+        'date_display' => '',
+        'display_relative' => FALSE,
+      ]
+    ));
+    $widget_instance = $facetReflection->getProperty('widgetInstance');
+    $widget_instance->setAccessible(TRUE);
+    $widget_instance->setValue($facet, $widget);
+
+    $query_type = new SearchApiDate(
+      [
+        'facet' => $facet,
+        'query' => $query,
+        'results' => $original_results,
+      ],
+      'search_api_string',
+      []
+    );
+
+    $built_facet = $query_type->build();
+    $this->assertInstanceOf('\Drupal\facets\FacetInterface', $built_facet);
+
+    $results = $built_facet->getResults();
+    $this->assertInternalType('array', $results);
+
+    foreach ($grouped_results as $k => $result) {
+      $this->assertInstanceOf('\Drupal\facets\Result\ResultInterface', $results[$k]);
+      $this->assertEquals($result['count'], $results[$k]->getCount());
+      $this->assertEquals($result['filter'], $results[$k]->getDisplayValue());
+    }
+  }
+
+  /**
+   * Data provider for date results and different groupings.
+   */
+  public function resultsProvider() {
+    return [
+      'Year' => [
+        SearchApiDate::FACETAPI_DATE_YEAR,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001' => ['count' => 1, 'filter' => 2001],
+          '2010' => ['count' => 2, 'filter' => 2010],
+          '2011' => ['count' => 1, 'filter' => 2011],
+          '2016' => ['count' => 10, 'filter' => 2016],
+        ],
+      ],
+      'Month' => [
+        SearchApiDate::FACETAPI_DATE_MONTH,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001-03' => ['count' => 1, 'filter' => 'March 2001'],
+          '2010-03' => ['count' => 2, 'filter' => 'March 2010'],
+          '2011-05' => ['count' => 1, 'filter' => 'May 2011'],
+          '2016-05' => ['count' => 8, 'filter' => 'May 2016'],
+          '2016-06' => ['count' => 2, 'filter' => 'June 2016'],
+        ],
+      ],
+      'Day' => [
+        SearchApiDate::FACETAPI_DATE_DAY,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001-03-16' => ['count' => 1, 'filter' => '16 March 2001'],
+          '2010-03-18' => ['count' => 1, 'filter' => '18 March 2010'],
+          '2010-03-31' => ['count' => 1, 'filter' => '31 March 2010'],
+          '2011-05-25' => ['count' => 1, 'filter' => '25 May 2011'],
+          '2016-05-25' => ['count' => 5, 'filter' => '25 May 2016'],
+          '2016-05-26' => ['count' => 3, 'filter' => '26 May 2016'],
+          '2016-06-03' => ['count' => 1, 'filter' => '03 June 2016'],
+          '2016-06-15' => ['count' => 1, 'filter' => '15 June 2016'],
+        ],
+      ],
+      'Hour' => [
+        SearchApiDate::FACETAPI_DATE_HOUR,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001-03-16T14' => ['count' => 1, 'filter' => '16/03/2001 14h'],
+          '2010-03-18T19' => ['count' => 1, 'filter' => '18/03/2010 19h'],
+          '2010-03-31T02' => ['count' => 1, 'filter' => '31/03/2010 02h'],
+          '2011-05-25T19' => ['count' => 1, 'filter' => '25/05/2011 19h'],
+          '2016-05-25T19' => ['count' => 3, 'filter' => '25/05/2016 19h'],
+          '2016-05-25T20' => ['count' => 1, 'filter' => '25/05/2016 20h'],
+          '2016-05-25T21' => ['count' => 1, 'filter' => '25/05/2016 21h'],
+          '2016-05-26T05' => ['count' => 1, 'filter' => '26/05/2016 05h'],
+          '2016-05-26T18' => ['count' => 2, 'filter' => '26/05/2016 18h'],
+          '2016-06-03T14' => ['count' => 1, 'filter' => '03/06/2016 14h'],
+          '2016-06-15T04' => ['count' => 1, 'filter' => '15/06/2016 04h'],
+        ],
+      ],
+      'Minute' => [
+        SearchApiDate::FACETAPI_DATE_MINUTE,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001-03-16T14:02' => ['count' => 1, 'filter' => '16/03/2001 14:02'],
+          '2010-03-18T19:22' => ['count' => 1, 'filter' => '18/03/2010 19:22'],
+          '2010-03-31T02:32' => ['count' => 1, 'filter' => '31/03/2010 02:32'],
+          '2011-05-25T19:12' => ['count' => 1, 'filter' => '25/05/2011 19:12'],
+          '2016-05-25T19:12' => ['count' => 3, 'filter' => '25/05/2016 19:12'],
+          '2016-05-25T20:30' => ['count' => 1, 'filter' => '25/05/2016 20:30'],
+          '2016-05-25T21:12' => ['count' => 1, 'filter' => '25/05/2016 21:12'],
+          '2016-05-26T05:00' => ['count' => 1, 'filter' => '26/05/2016 05:00'],
+          '2016-05-26T18:10' => ['count' => 2, 'filter' => '26/05/2016 18:10'],
+          '2016-06-03T14:05' => ['count' => 1, 'filter' => '03/06/2016 14:05'],
+          '2016-06-15T04:54' => ['count' => 1, 'filter' => '15/06/2016 04:54'],
+        ],
+      ],
+      'Second' => [
+        SearchApiDate::FACETAPI_DATE_SECOND,
+        [
+          ['count' => 1, 'filter' => '984711763'],
+          ['count' => 1, 'filter' => '1268900542'],
+          ['count' => 1, 'filter' => '1269963121'],
+          ['count' => 1, 'filter' => '1306314733'],
+          ['count' => 1, 'filter' => '1464167533'],
+          ['count' => 2, 'filter' => '1464167534'],
+          ['count' => 1, 'filter' => '1464172214'],
+          ['count' => 1, 'filter' => '1464174734'],
+          ['count' => 1, 'filter' => '1464202800'],
+          ['count' => 1, 'filter' => '1464250210'],
+          ['count' => 1, 'filter' => '1464250230'],
+          ['count' => 1, 'filter' => '1464926723'],
+          ['count' => 1, 'filter' => '1465930475'],
+        ],
+        [
+          '2001-03-16T14:02:43' => ['count' => 1, 'filter' => '16/03/2001 14:02:43'],
+          '2010-03-18T19:22:22' => ['count' => 1, 'filter' => '18/03/2010 19:22:22'],
+          '2010-03-31T02:32:01' => ['count' => 1, 'filter' => '31/03/2010 02:32:01'],
+          '2011-05-25T19:12:13' => ['count' => 1, 'filter' => '25/05/2011 19:12:13'],
+          '2016-05-25T19:12:13' => ['count' => 1, 'filter' => '25/05/2016 19:12:13'],
+          '2016-05-25T19:12:14' => ['count' => 2, 'filter' => '25/05/2016 19:12:14'],
+          '2016-05-25T20:30:14' => ['count' => 1, 'filter' => '25/05/2016 20:30:14'],
+          '2016-05-25T21:12:14' => ['count' => 1, 'filter' => '25/05/2016 21:12:14'],
+          '2016-05-26T05:00:00' => ['count' => 1, 'filter' => '26/05/2016 05:00:00'],
+          '2016-05-26T18:10:10' => ['count' => 1, 'filter' => '26/05/2016 18:10:10'],
+          '2016-05-26T18:10:30' => ['count' => 1, 'filter' => '26/05/2016 18:10:30'],
+          '2016-06-03T14:05:23' => ['count' => 1, 'filter' => '03/06/2016 14:05:23'],
+          '2016-06-15T04:54:35' => ['count' => 1, 'filter' => '15/06/2016 04:54:35'],
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * Tests string query type without results.
+   */
+  public function testEmptyResults() {
+    $query = new SearchApiQuery([], 'search_api_query', []);
+    $facet = new Facet([], 'facets_facet');
+
+    $query_type = new SearchApiDate(
+      [
+        'facet' => $facet,
+        'query' => $query,
+      ],
+      'search_api_string',
+      []
+    );
+
+    $built_facet = $query_type->build();
+    $this->assertInstanceOf('\Drupal\facets\FacetInterface', $built_facet);
+
+    $results = $built_facet->getResults();
+    $this->assertInternalType('array', $results);
+    $this->assertEmpty($results);
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/tests/src/Unit/Plugin/query_type/SearchApiGranularTest.php
@@ -0,0 +1,96 @@
+<?php
+
+namespace Drupal\Tests\facets\Unit\Plugin\query_type;
+
+use Drupal\facets\Entity\Facet;
+use Drupal\facets\Plugin\facets\query_type\SearchApiGranular;
+use Drupal\search_api\Plugin\views\query\SearchApiQuery;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Unit test for granular query type.
+ *
+ * @group facets
+ */
+class SearchApiGranularTest extends UnitTestCase {
+
+  /**
+   * Tests string query type without executing the query with an "AND" operator.
+   */
+  public function testQueryTypeAnd() {
+    $query = new SearchApiQuery([], 'search_api_query', []);
+    $facetReflection = new \ReflectionClass ('Drupal\facets\Entity\Facet');
+    $facet = new Facet(
+      ['query_operator' => 'AND'],
+      'facets_facet'
+    );
+    $widget = $this->getMockBuilder('Drupal\facets\Widget\WidgetPluginInterface')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $widget->method('getConfiguration')->will($this->returnValue(['granularity' => 10]));
+    $widget_instance = $facetReflection->getProperty('widgetInstance');
+    $widget_instance->setAccessible(TRUE);
+    $widget_instance->setValue($facet, $widget);
+
+    // Results for the widget.
+    $original_results = [
+      ['count' => 3, 'filter' => '2'],
+      ['count' => 5, 'filter' => '4'],
+      ['count' => 7, 'filter' => '9'],
+      ['count' => 9, 'filter' => '11'],
+    ];
+
+    // Facets the widget should produce.
+    $grouped_results = [
+      0 => ['count' => 15, 'filter' => '0'],
+      10 => ['count' => 9, 'filter' => 10],
+    ];
+
+    $query_type = new SearchApiGranular(
+      [
+        'facet' => $facet,
+        'query' => $query,
+        'results' => $original_results,
+      ],
+      'search_api_string',
+      []
+    );
+
+    $built_facet = $query_type->build();
+    $this->assertInstanceOf('\Drupal\facets\FacetInterface', $built_facet);
+
+    $results = $built_facet->getResults();
+    $this->assertInternalType('array', $results);
+
+    foreach ($grouped_results as $k => $result) {
+      $this->assertInstanceOf('\Drupal\facets\Result\ResultInterface', $results[$k]);
+      $this->assertEquals($result['count'], $results[$k]->getCount());
+      $this->assertEquals($result['filter'], $results[$k]->getDisplayValue());
+    }
+  }
+
+  /**
+   * Tests string query type without results.
+   */
+  public function testEmptyResults() {
+    $query = new SearchApiQuery([], 'search_api_query', []);
+    $facet = new Facet([], 'facets_facet');
+
+    $query_type = new SearchApiGranular(
+      [
+        'facet' => $facet,
+        'query' => $query,
+      ],
+      'search_api_string',
+      []
+    );
+
+    $built_facet = $query_type->build();
+    $this->assertInstanceOf('\Drupal\facets\FacetInterface', $built_facet);
+
+    $results = $built_facet->getResults();
+    $this->assertInternalType('array', $results);
+    $this->assertEmpty($results);
+  }
+
+}