diff --git a/core_search_facets/src/Plugin/facets/query_type/CoreNodeSearchDate.php b/core_search_facets/src/Plugin/facets/query_type/CoreNodeSearchDate.php
index 54950c6..ce894f7 100644
--- a/core_search_facets/src/Plugin/facets/query_type/CoreNodeSearchDate.php
+++ b/core_search_facets/src/Plugin/facets/query_type/CoreNodeSearchDate.php
@@ -15,7 +15,7 @@ use Drupal\facets\Result\Result;
  *
  * @FacetsQueryType(
  *   id = "core_node_search_date",
- *   label = @Translation("String"),
+ *   label = @Translation("Date"),
  * )
  */
 class CoreNodeSearchDate extends QueryTypePluginBase {
@@ -31,6 +31,9 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
    * {@inheritdoc}
    */
   public function execute() {
+    /** @var \Drupal\facets\Utility\FacetsDateHandler $date_handler */
+    $date_handler = \Drupal::getContainer()->get('facets.utility.date_handler');
+
     /** @var \Drupal\core_search_facets\Plugin\CoreSearchFacetSourceInterface $facet_source */
     $facet_source = $this->facet->getFacetSource();
 
@@ -40,9 +43,6 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
       return;
     }
 
-    /** @var \Drupal\facets\Utility\FacetsDate $facets_date */
-    $facets_date = \Drupal::getContainer()->get('facets.utility.date');
-
     // Gets facet query and this facet's query info.
     /** @var \Drupal\core_search_facets\FacetsQuery $facet_query */
     $facet_query = $facet_source->getFacetQueryExtender();
@@ -50,7 +50,7 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
     $tables_joined = [];
 
     // Obtain the start and end dates.
-    if (preg_match($facets_date::FACETS_REGEX_DATE_RANGE, $active_item, $matches)) {
+    if (preg_match($date_handler::FACETS_REGEX_DATE_RANGE, $active_item, $matches)) {
       $start = strtotime($matches[1]);
       $end = strtotime($matches[8]);
     }
@@ -82,15 +82,9 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
    * {@inheritdoc}
    */
   public function build() {
-
-    /** @var \Drupal\facets\Utility\FacetsDate $facets_date */
-    $facets_date = \Drupal::getContainer()->get('facets.utility.date');
-
-    // Makes sure there was at least one match.
-    /*if (!$this->adapter->hasMatches) {
-      return array();
-    }*/
-
+    /** @var \Drupal\facets\Utility\FacetsDateHandler $date_handler */
+    $date_handler = \Drupal::getContainer()->get('facets.utility.date_handler');
+    
     // Gets base facet query, adds facet field and filters.
     /* @var \Drupal\core_search_facets\Plugin\CoreSearchFacetSourceInterface $facet_source */
     $facet_source = $this->facet->getFacetSource();
@@ -122,12 +116,12 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
         /*$build[$value] = array('#count' => $this->facet->getResultCount());
 
         // Gets next "gap" increment, mintue being the lowest be can go.
-        $date_gap = facetapi_get_date_gap($item['start'], $item['end']);
-        $gap = facetapi_get_next_date_gap($date_gap, FACETAPI_DATE_MINUTE);
+        $date_gap = facets_get_date_gap($item['start'], $item['end']);
+        $gap = facetsGetNextDateGap($date_gap, facets_DATE_MINUTE);
 
         // If there is a previous item, there is a parent, uses a reference so the
         // arrays are populated when they are updated.
-        if (NULL !== $parent) {
+        if (is_null($parent)) {
           $build[$parent]['#item_children'][$value] = &$build[$value];
           $build[$value]['#item_parents'][$parent] = $parent;
         }
@@ -138,20 +132,19 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
 
       // Mind the gap! Calculates gap from min and max timestamps.
       $timestamps = array_keys($raw_values);
-      if (NULL === $parent) {
+      if (is_null($parent)) {
         if (count($raw_values) > 1) {
-          // @TODO for the moment hard-coding the gap.
-          $gap = $facets_date::FACETS_DATE_DAY;
+          $gap = $date_handler::FACETS_DATE_DAY;// $date_handler->facetsGetTimestampGap(min($timestamps), max($timestamps));//
         }
         else {
-          $gap = $facets_date::FACETS_DATE_HOUR;
+          $gap = $date_handler::FACETS_DATE_HOUR;
         }
       }
 
       // Converts all timestamps to dates in ISO 8601 format.
       $dates = [];
       foreach ($timestamps as $timestamp) {
-        $dates[$timestamp] = $facets_date->isoDate($timestamp, $gap);
+        $dates[$timestamp] = $date_handler->isoDate($timestamp, $gap);
       }
 
       // Treat each date as the range start and next date as the range end.
@@ -159,11 +152,11 @@ class CoreNodeSearchDate extends QueryTypePluginBase {
       $previous = NULL;
       foreach (array_unique($dates) as $date) {
         if (is_null($previous)) {
-          $range_end[$previous] = $facets_date->getNextDateIncrement($previous, $gap);
+          $range_end[$previous] = $date_handler->getNextDateIncrement($previous, $gap);
         }
         $previous = $date;
       }
-      $range_end[$previous] = $facets_date->getNextDateIncrement($previous, $gap);
+      $range_end[$previous] = $date_handler->getNextDateIncrement($previous, $gap);
 
       $facet_results = [];
       foreach ($raw_values as $value => $count) {
diff --git a/facets.module b/facets.module
index 7f9cafb..199188f 100644
--- a/facets.module
+++ b/facets.module
@@ -8,8 +8,6 @@
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\search_api\Query\QueryInterface;
 
-module_load_include('date.inc', 'facets');
-
 /**
  * Implements hook_help().
  */
diff --git a/facets.services.yml b/facets.services.yml
index f9693d9..7432eed 100644
--- a/facets.services.yml
+++ b/facets.services.yml
@@ -22,5 +22,5 @@ services:
       - '@plugin.manager.facets.facet_source'
       - '@plugin.manager.facets.processor'
       - '@entity_type.manager'
-  facets.utility.date:
-    class: Drupal\facets\Utility\FacetsDate
+  facets.utility.date_handler:
+    class: Drupal\facets\utility\FacetsDateHandler
diff --git a/src/QueryType/QueryTypePluginBase.php b/src/QueryType/QueryTypePluginBase.php
index 0d2eff7..01f0b33 100644
--- a/src/QueryType/QueryTypePluginBase.php
+++ b/src/QueryType/QueryTypePluginBase.php
@@ -65,13 +65,6 @@ abstract class QueryTypePluginBase extends PluginBase implements QueryTypeInterf
   /**
    * {@inheritdoc}
    */
-  public function extractAdditionalInfo() {
-    return [];
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function getConfiguration() {
     return $this->configuration;
   }
diff --git a/src/Utility/FacetsDate.php b/src/Utility/FacetsDate.php
deleted file mode 100644
index 37b53a2..0000000
--- a/src/Utility/FacetsDate.php
+++ /dev/null
@@ -1,380 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains Drupal\facets\Utility\FacetsDate.
- */
-
-namespace Drupal\facets\Utility;
-
-/**
- * Helpers for dates.
- */
-class FacetsDate {
-
-  /**
-   * String that represents a time gap of a year between two dates.
-   */
-  const FACETS_DATE_YEAR = 'YEAR';
-
-  /**
-   * String that represents a time gap of a month between two dates.
-   */
-  const FACETS_DATE_MONTH = 'MONTH';
-
-  /**
-   * String that represents a time gap of a day between two dates.
-   */
-  const FACETS_DATE_DAY = 'DAY';
-
-  /**
-   * String that represents a time gap of an hour between two dates.
-   */
-  const FACETS_DATE_HOUR = 'HOUR';
-
-  /**
-   * String that represents a time gap of a minute between two dates.
-   */
-  const FACETS_DATE_MINUTE = 'MINUTE';
-
-  /**
-   * String that represents a time gap of a second between two dates.
-   */
-  const FACETS_DATE_SECOND = 'SECOND';
-
-  /**
-   * Date string for ISO 8601 date formats.
-   */
-  const FACETS_DATE_ISO8601 = 'Y-m-d\TH:i:s\Z';
-
-  /**
-   * Regex pattern for range queries.
-   */
-  const FACETS_REGEX_RANGE = '/^[\[\{](\S+) TO (\S+)[\]\}]$/';
-
-  /**
-   * Regex pattern for date queries.
-   */
-  const FACETS_REGEX_DATE = '/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/';
-
-  /**
-   * Regex pattern for date ranges.
-   */
-  const FACETS_REGEX_DATE_RANGE = '/^\[(/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/) TO (/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/)\]$/';
-
-  /**
-   * Converts dates from unix timestamps to ISO 8601 format.
-   *
-   * @param int $timestamp
-   *   An integer containing the Unix timestamp being converted.
-   * @param string $gap
-   *   A string containing the gap, see FACETS_DATE_* constants for valid
-   *   values. Defaults to self::FACETS_DATE_SECOND.
-   *
-   * @return string
-   *   A string containing the date in ISO 8601 format.
-   */
-  public function isoDate($timestamp, $gap = self::FACETS_DATE_SECOND) {
-    switch ($gap) {
-      case static::FACETS_DATE_SECOND:
-        $format = static::FACETS_DATE_ISO8601;
-        break;
-
-      case static::FACETS_DATE_MINUTE:
-        $format = 'Y-m-d\TH:i:00\Z';
-        break;
-
-      case static::FACETS_DATE_HOUR:
-        $format = 'Y-m-d\TH:00:00\Z';
-        break;
-
-      case static::FACETS_DATE_DAY:
-        $format = 'Y-m-d\T00:00:00\Z';
-        break;
-
-      case static::FACETS_DATE_MONTH:
-        $format = 'Y-m-01\T00:00:00\Z';
-        break;
-
-      case static::FACETS_DATE_YEAR:
-        $format = 'Y-01-01\T00:00:00\Z';
-        break;
-
-      default:
-        $format = static::FACETS_DATE_ISO8601;
-        break;
-    }
-    return gmdate($format, $timestamp);
-  }
-
-  /**
-   * Returns a date gap one increment smaller than the one passed.
-   *
-   * @param string $gap
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values.
-   * @param string $min_gap
-   *   A string containing the the minimum gap that can be returned, defaults to
-   *   FACETAPI_DATE_SECOND. This is useful for defining the smallest increment
-   *   that can be used in a date drilldown.
-   *
-   * @return string
-   *   A string containing the smaller date gap, NULL if there is no smaller gap.
-   *   See FACETAPI_DATE_* constants for valid values.
-   */
-  public function getNextDateGap($gap, $min_gap = self::FACETS_DATE_SECOND) {
-    // Array of numbers used to determine whether the next gap is smaller than
-    // the minimum gap allowed in the drilldown.
-    $gap_numbers = [
-      static::FACETS_DATE_YEAR => 6,
-      static::FACETS_DATE_MONTH => 5,
-      static::FACETS_DATE_DAY => 4,
-      static::FACETS_DATE_HOUR => 3,
-      static::FACETS_DATE_MINUTE => 2,
-      static::FACETS_DATE_SECOND => 1,
-    ];
-
-    // Gets gap numbers for both the gap and minimum gap, checks if the next gap
-    // is within the limit set by the $min_gap parameter.
-    $gap_num = isset($gap_numbers[$gap]) ? $gap_numbers[$gap] : 6;
-    $min_num = isset($gap_numbers[$min_gap]) ? $gap_numbers[$min_gap] : 1;
-
-    return ($gap_num > $min_num) ? array_search($gap_num - 1, $gap_numbers) : $min_gap;
-  }
-
-  /**
-   * Determines the best search gap to use for an arbitrary date range.
-   *
-   * Generally, we use the maximum gap that fits between the start and end date.
-   * If they are more than a year apart, 1 year; if they are more than a month
-   * apart, 1 month; etc.
-   *
-   * This function uses Unix timestamps for its computation and so is not useful
-   * for dates outside that range.
-   *
-   * @param int $start_time
-   *   A string containing the start date as an ISO date string.
-   * @param int $end_time
-   *   A string containing the end date as an ISO date string.
-   * @param string|NULL $min_gap
-   *   (Optional) The minimum gap that should be returned.
-   *
-   * @return string
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values. Returns FALSE of either of the dates cannot be converted to a
-   *   timestamp.
-   */
-  public function getTimestampGap($start_time, $end_time, $min_gap = NULL) {
-    $time_diff = $end_time - $start_time;
-
-    switch (TRUE) {
-      // NOTE: 31536000 == 60 * 60 * 24 * 365
-      case ($time_diff >= 31536000):
-        $gap = static::FACETS_DATE_YEAR;
-        break;
-
-      case ($time_diff >= 86400 * gmdate('t', $start_time)):
-        $gap = static::FACETS_DATE_MONTH;
-        break;
-
-      case ($time_diff >= 86400):
-        $gap = static::FACETS_DATE_DAY;
-        break;
-
-      case ($time_diff >= 3600):
-        $gap = static::FACETS_DATE_HOUR;
-        break;
-
-      case ($time_diff >= 60):
-        $gap = static::FACETS_DATE_MINUTE;
-        break;
-
-      default:
-        $gap = static::FACETS_DATE_SECOND;
-        break;
-    }
-
-    // Return the calculated gap if a minimum gap was not passed of the calculated
-    // gap is a larger interval than the minimum gap.
-    if (is_null($min_gap) || $this->dateGapCompare($gap, $min_gap) >= 0) {
-      return $gap;
-    }
-    else {
-      return $min_gap;
-    }
-  }
-
-  /**
-   * Converts ISO date strings to Unix timestamps.
-   *
-   * The ::facetapi_get_timestamp_gap() function is used to calculate the gap.
-   *
-   * @param string $start_date
-   *   A string containing the start date as an ISO date string.
-   * @param string $end_date
-   *   A string containing the end date as an ISO date string.
-   * @param string|NULL $min_gap
-   *   (Optional) The minimum gap that should be returned.
-   *
-   * @return string|bool
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values. Returns FALSE of either of the dates cannot be converted to a
-   *   timestamp.
-   *
-   * @see getTimestampGap()
-   */
-  public function getDateGap($start_date, $end_date, $min_gap = NULL) {
-    $range = [strtotime($start_date), strtotime($end_date)];
-
-    if (!in_array(FALSE, $range, TRUE)) {
-      return $this->getTimestampGap($range[0], $range[1], $min_gap);
-    }
-    return FALSE;
-  }
-
-  /**
-   * Returns a formatted date based on the passed timestamp and gap.
-   *
-   * This function assumes that gaps less than one day will be displayed in a
-   * search context in which a larger containing gap including a day is already
-   * displayed. So, HOUR, MINUTE, and SECOND gaps only display time information,
-   * without date.
-   *
-   * @param int $timestamp
-   *   An integer containing the Unix timestamp.
-   * @param string $gap
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values, defaults to YEAR.
-   *
-   * @return
-   *   A gap-appropriate display date used in the facet link.
-   */
-  public function formatTimestamp($timestamp, $gap = self::FACETS_DATE_YEAR) {
-    switch ($gap) {
-      case static::FACETS_DATE_MONTH:
-        return format_date($timestamp, 'custom', 'F Y', 'UTC');
-
-      case static::FACETS_DATE_DAY:
-        return format_date($timestamp, 'custom', 'F j, Y', 'UTC');
-
-      case static::FACETS_DATE_HOUR:
-        return format_date($timestamp, 'custom', 'g A', 'UTC');
-
-      case static::FACETS_DATE_MINUTE:
-        return format_date($timestamp, 'custom', 'g:i A', 'UTC');
-
-      case static::FACETS_DATE_SECOND:
-        return format_date($timestamp, 'custom', 'g:i:s A', 'UTC');
-
-      default:
-        return format_date($timestamp, 'custom', 'Y', 'UTC');
-    }
-  }
-
-  /**
-   * Returns a formatted date based on the passed ISO date string and gap.
-   *
-   * @param string $date
-   *   A string containing the date as an ISO date string.
-   * @param string $gap
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values, defaults to YEAR.
-   * @param string $callback
-   *   The formatting callback, defaults to "facets_format_timestamp".
-   *
-   * @return
-   *   A gap-appropriate display date used in the facet link.
-   *
-   * @see facetsFormatTimestamp()
-   */
-  public function facetsFormatDate($date, $gap = self::FACETS_DATE_YEAR, $callback = 'facets_format_timestamp') {
-    $timestamp = strtotime($date);
-    return $callback($timestamp, $gap);
-  }
-
-  /**
-   * Returns the next increment from the given ISO date and gap. This function is
-   * useful for getting the upper limit of a date range from the given start
-   * date.
-   *
-   * @param string $date
-   *   A string containing the date as an ISO date string.
-   * @param string $gap
-   *   A string containing the gap, see FACETAPI_DATE_* constants for valid
-   *   values, defaults to YEAR.
-   *
-   * @return
-   *   A string containing the date, FALSE if the passed date could not be parsed.
-   */
-  public function getNextDateIncrement($date, $gap) {
-    if (preg_match(static::FACETS_REGEX_DATE, $date, $match)) {
-
-      // Increments the timestamp.
-      switch ($gap) {
-        case static::FACETS_DATE_MONTH:
-          $match[2] += 1;
-          break;
-        case static::FACETS_DATE_DAY:
-          $match[3] += 1;
-          break;
-        case static::FACETS_DATE_HOUR:
-          $match[4] += 1;
-          break;
-        case static::FACETS_DATE_MINUTE:
-          $match[5] += 1;
-          break;
-        case static::FACETS_DATE_SECOND:
-          $match[6] += 1;
-          break;
-        default:
-          $match[1] += 1;
-          break;
-      }
-
-      // Gets the next incremenet.
-      $time = gmmktime(
-        $match[4],
-        $match[5],
-        $match[6],
-        $match[2],
-        $match[3],
-        $match[1]
-      );
-      return $this->isoDate($time);
-    }
-    return FALSE;
-  }
-
-  /**
-   * Compares two timestamp gaps.
-   *
-   * @param string $gap1
-   * @param string $gap2
-   *
-   * @return int
-   *   Returns -1 if gap1 is less than gap2, 1 if gap1 is greater than gap2, and 0
-   *   if they are equal.
-   */
-  public function dateGapCompare($gap1, $gap2) {
-
-    $gap_numbers = [
-      static::FACETS_DATE_YEAR => 6,
-      static::FACETS_DATE_MONTH => 5,
-      static::FACETS_DATE_DAY => 4,
-      static::FACETS_DATE_HOUR => 3,
-      static::FACETS_DATE_MINUTE => 2,
-      static::FACETS_DATE_SECOND => 1,
-    ];
-
-    $gap1_num = isset($gap_numbers[$gap1]) ? $gap_numbers[$gap1] : 6;
-    $gap2_num = isset($gap_numbers[$gap2]) ? $gap_numbers[$gap2] : 6;
-
-    if ($gap1_num == $gap2_num) {
-      return 0;
-    }
-    else {
-      return ($gap1_num < $gap2_num) ? -1 : 1;
-    }
-  }
-
-}
diff --git a/src/Utility/FacetsDateHandler.php b/src/Utility/FacetsDateHandler.php
new file mode 100644
index 0000000..de98ed1
--- /dev/null
+++ b/src/Utility/FacetsDateHandler.php
@@ -0,0 +1,370 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\facets\FacetsDateHandler.
+ */
+
+namespace Drupal\facets\utility;
+
+/**
+ * Dates Handler service.
+ */
+class FacetsDateHandler {
+
+  /**
+   * String that represents a time gap of a day between two dates.
+   */
+ const FACETS_DATE_DAY = 'DAY';
+
+  /**
+   * String that represents a time gap of a year between two dates.
+   */
+  const FACETS_DATE_YEAR = 'YEAR';
+
+  /**
+   * String that represents a time gap of a month between two dates.
+   */
+   const FACETS_DATE_MONTH = 'MONTH';
+
+  /**
+   * String that represents a time gap of an hour between two dates.
+   */
+   const FACETS_DATE_HOUR = 'HOUR';
+
+  /**
+   * String that represents a time gap of a minute between two dates.
+   */
+   const FACETS_DATE_MINUTE = 'MINUTE';
+
+  /**
+   * String that represents a time gap of a second between two dates.
+   */
+   const FACETS_DATE_SECOND = 'SECOND';
+
+  /**
+   * Date string for ISO 8601 date formats.
+   */
+   const FACETS_DATE_ISO8601 = 'Y-m-d\TH:i:s\Z';
+
+  /**
+   * Regex pattern for range queries.
+   */
+   const FACETS_REGEX_RANGE = '/^[\[\{](\S+) TO (\S+)[\]\}]$/';
+
+  /**
+   * Regex pattern for date queries.
+   */
+   const FACETS_REGEX_DATE = '/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/';
+
+  /**
+   * Regex pattern for date ranges.
+   */
+  const FACETS_REGEX_DATE_RANGE = '/^\[(/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/) TO (/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/)\]$/';
+
+  /**
+   * Converts dates from Unix timestamps into ISO 8601 format.
+   *
+   * @param int $timestamp
+   *   An integer containing the Unix timestamp being converted.
+   * @param string $gap
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values. Defaults to FACETS_DATE_SECOND.
+   *
+   * @return string
+   *   A string containing the date in ISO 8601 format.
+   */
+  public function isoDate($timestamp, $gap = 'SECOND') {
+    switch ($gap) {
+      case static::FACETS_DATE_SECOND:
+        $format = static::FACETS_DATE_ISO8601;
+        break;
+
+      case static::FACETS_DATE_MINUTE:
+        $format = 'Y-m-d\TH:i:00\Z';
+        break;
+
+      case static::FACETS_DATE_HOUR:
+        $format = 'Y-m-d\TH:00:00\Z';
+        break;
+
+      case static::FACETS_DATE_DAY:
+        $format = 'Y-m-d\T00:00:00\Z';
+        break;
+
+      case static::FACETS_DATE_MONTH:
+        $format = 'Y-m-01\T00:00:00\Z';
+        break;
+
+      case static::FACETS_DATE_YEAR:
+        $format = 'Y-01-01\T00:00:00\Z';
+        break;
+
+      default:
+        $format = static::FACETS_DATE_ISO8601;
+        break;
+    }
+    return gmdate($format, $timestamp);
+  }
+
+  /**
+   * Return a date gap one increment smaller than the one passed.
+   *
+   * @param string $gap
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values.
+   * @param string $min_gap
+   *   A string containing the the minimum gap that can be returned, defaults to
+   *   FACETS_DATE_SECOND. This is useful for defining the smallest increment
+   *   that can be used in a date drilldown.
+   *
+   * @return string
+   *   A string containing the smaller date gap, NULL if there is no smaller gap.
+   *   See FACETS_DATE_* constants for valid values.
+   */
+  public function getNextDateGap($gap, $min_gap = self::FACETS_DATE_SECOND) {
+    // Array of numbers used to determine whether the next gap is smaller than
+    // the minimum gap allowed in the drilldown.
+    $gap_numbers = array(
+      static::FACETS_DATE_YEAR => 6,
+      static::FACETS_DATE_MONTH => 5,
+      static::FACETS_DATE_DAY => 4,
+      static::FACETS_DATE_HOUR => 3,
+      static::FACETS_DATE_MINUTE => 2,
+      static::FACETS_DATE_SECOND => 1,
+    );
+
+    // Gets gap numbers for both the gap and minimum gap, checks if the next gap
+    // is within the limit set by the $min_gap parameter.
+    $gap_num = isset($gap_numbers[$gap]) ? $gap_numbers[$gap] : 6;
+    $min_num = isset($gap_numbers[$min_gap]) ? $gap_numbers[$min_gap] : 1;
+    return ($gap_num > $min_num) ? array_search($gap_num - 1, $gap_numbers) : $min_gap;
+  }
+
+  /**
+   * Determines the best search gap to use for an arbitrary date range.
+   *
+   * Generally, we use the maximum gap that fits between the start and end date.
+   * If they are more than a year apart, 1 year; if they are more than a month
+   * apart, 1 month; etc.
+   *
+   * This function uses Unix timestamps for its computation and so is not useful
+   * for dates outside that range.
+   *
+   * @param int $start_time
+   *   A string containing the start date as an ISO date string.
+   * @param int $end_time
+   *   A string containing the end date as an ISO date string.
+   * @param string|NULL $min_gap
+   *   (Optional) The minimum gap that should be returned.
+   *
+   * @return string
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values. Returns FALSE of either of the dates cannot be converted to a
+   *   timestamp.
+   */
+  public function getTimestampGap($start_time, $end_time, $min_gap = NULL) {
+    $time_diff = $end_time - $start_time;
+    switch (TRUE) {
+      // NOTE: 31536000 == 60 * 60 * 24 * 365
+      case ($time_diff >= 31536000):
+        $gap = static::FACETS_DATE_YEAR;
+        break;
+
+      case ($time_diff >= 86400 * gmdate('t', $start_time)):
+        $gap = static::FACETS_DATE_MONTH;
+        break;
+
+      case ($time_diff >= 86400):
+        $gap = static::FACETS_DATE_DAY;
+        break;
+
+      case ($time_diff >= 3600):
+        $gap = static::FACETS_DATE_HOUR;
+        break;
+
+      case ($time_diff >= 60):
+        $gap = static::FACETS_DATE_MINUTE;
+        break;
+
+      default:
+        $gap = static::FACETS_DATE_SECOND;
+        break;
+    }
+
+    // Return the calculated gap if a minimum gap was not passed of the calculated
+    // gap is a larger interval than the minimum gap.
+    if (is_null($min_gap) || $this->gapCompare($gap, $min_gap) >= 0) {
+      return $gap;
+    }
+    else {
+      return $min_gap;
+    }
+  }
+
+  /**
+   * Converts ISO date strings to Unix timestamps, passes values to the
+   * FACETS_get_timestamp_gap() function to calculate the gap.
+   *
+   * @param string $start_date
+   *   A string containing the start date as an ISO date string.
+   * @param string $end_date
+   *   A string containing the end date as an ISO date string.
+   * @param string|NULL $min_gap
+   *   (Optional) The minimum gap that should be returned.
+   *
+   * @return string
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values. Returns FALSE of either of the dates cannot be converted to a
+   *   timestamp.
+   *
+   * @see FACETS_get_timestamp_gap()
+   */
+  public function getDateGap($start_date, $end_date, $min_gap = NULL) {
+    $range = array(strtotime($start_date), strtotime($end_date));
+    if (!in_array(FALSE, $range, TRUE)) {
+      return $this->getTimestampGap($range[0], $range[1], $min_gap);
+    }
+    return FALSE;
+  }
+
+  /**
+   * Returns a formatted date based on the passed timestamp and gap.
+   *
+   * This function assumes that gaps less than one day will be displayed in a
+   * search context in which a larger containing gap including a day is already
+   * displayed. So, HOUR, MINUTE, and SECOND gaps only display time information,
+   * without date.
+   *
+   * @param int $timestamp
+   *   An integer containing the Unix timestamp.
+   * @param string $gap
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values, defaults to YEAR.
+   *
+   * @return string
+   *   A gap-appropriate display date used in the facet link.
+   */
+  public function formatTimestamp($timestamp, $gap = FACETS_DATE_YEAR) {
+    switch ($gap) {
+      case static::FACETS_DATE_MONTH:
+        return format_date($timestamp, 'custom', 'F Y', 'UTC');
+
+      case static::FACETS_DATE_DAY:
+        return format_date($timestamp, 'custom', 'F j, Y', 'UTC');
+
+      case static::FACETS_DATE_HOUR:
+        return format_date($timestamp, 'custom', 'g A', 'UTC');
+
+      case static::FACETS_DATE_MINUTE:
+        return format_date($timestamp, 'custom', 'g:i A', 'UTC');
+
+      case static::FACETS_DATE_SECOND:
+        return format_date($timestamp, 'custom', 'g:i:s A', 'UTC');
+
+      default:
+        return format_date($timestamp, 'custom', 'Y', 'UTC');
+    }
+  }
+
+  /**
+   * Returns a formatted date based on the passed ISO date string and gap.
+   *
+   * @param $date
+   *   A string containing the date as an ISO date string.
+   * @param $gap
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values, defaults to YEAR.
+   * @param $callback
+   *   The formatting callback, defaults to "FACETS_format_timestamp".
+   *
+   * @return
+   *   A gap-appropriate display date used in the facet link.
+   *
+   * @see FACETS_format_timestamp()
+   */
+  public function formatDate($date, $gap = self::FACETS_DATE_YEAR, $callback = 'facets_format_timestamp') {
+    $timestamp = strtotime($date);
+    return $callback($timestamp, $gap);
+  }
+
+  /**
+   * Returns the next increment from the given ISO date and gap. This function is
+   * useful for getting the upper limit of a date range from the given start
+   * date.
+   *
+   * @param string $date
+   *   A string containing the date as an ISO date string.
+   * @param string $gap
+   *   A string containing the gap, see FACETS_DATE_* constants for valid
+   *   values, defaults to YEAR.
+   *
+   * @return string
+   *   A string containing the date, FALSE if the passed date could not be parsed.
+   */
+  public function getNextDateIncrement($date, $gap) {
+    if (preg_match(static::FACETS_REGEX_DATE, $date, $match)) {
+
+      // Increments the timestamp.
+      switch ($gap) {
+        case static::FACETS_DATE_MONTH:
+          $match[2] += 1;
+          break;
+        case static::FACETS_DATE_DAY:
+          $match[3] += 1;
+          break;
+        case static::FACETS_DATE_HOUR:
+          $match[4] += 1;
+          break;
+        case static::FACETS_DATE_MINUTE:
+          $match[5] += 1;
+          break;
+        case static::FACETS_DATE_SECOND:
+          $match[6] += 1;
+          break;
+        default:
+          $match[1] += 1;
+          break;
+      }
+
+      // Gets the next increment.
+      return $this->isoDate(
+        gmmktime($match[4], $match[5], $match[6], $match[2], $match[3], $match[1])
+      );
+    }
+    return FALSE;
+  }
+
+  /**
+   * Compares two timestamp gaps.
+   *
+   * @param string $gap1
+   * @param string $gap2
+   *
+   * @return int
+   *   Returns -1 if gap1 is less than gap2, 1 if gap1 is greater than gap2, and 0
+   *   if they are equal.
+   */
+  public function gapCompare($gap1, $gap2) {
+
+    $gap_numbers = array(
+      static::FACETS_DATE_YEAR => 6,
+      static::FACETS_DATE_MONTH => 5,
+      static::FACETS_DATE_DAY => 4,
+      static::FACETS_DATE_HOUR => 3,
+      static::FACETS_DATE_MINUTE => 2,
+      static::FACETS_DATE_SECOND => 1,
+    );
+
+    $gap1_num = isset($gap_numbers[$gap1]) ? $gap_numbers[$gap1] : 6;
+    $gap2_num = isset($gap_numbers[$gap2]) ? $gap_numbers[$gap2] : 6;
+
+    if ($gap1_num == $gap2_num) {
+      return 0;
+    }
+    else {
+      return ($gap1_num < $gap2_num) ? -1 : 1;
+    }
+  }
+}
+
diff --git a/tests/src/Unit/Utility/FacetsDateHandlerTest.php b/tests/src/Unit/Utility/FacetsDateHandlerTest.php
new file mode 100644
index 0000000..0ac9739
--- /dev/null
+++ b/tests/src/Unit/Utility/FacetsDateHandlerTest.php
@@ -0,0 +1,194 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\facets\Unit\utility\FacetsDateHandlerTest.
+ */
+
+namespace Drupal\Tests\facets\Unit\utility;
+
+use Drupal\facets\utility\FacetsDateHandler;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Unit test for Date Handler Service.
+ *
+ * @group facets
+ */
+class FacetsDateHandlerTest extends UnitTestCase {
+
+  /**
+   * Timestamp used by tests: Thu, 26 Nov 1987 20:43:04 GMT
+   */
+  const TIMESTAMP = 564957784;
+
+  /**
+   * ISO date used by tests: Thu, 26 Nov 1987 20:43:04 GMT
+   */
+  const ISO_DATE = '1987-11-26T20:43:04Z';
+
+  /**
+   * Tests the isoDate method.
+   *
+   * @dataProvider provideIsoDates
+   */
+  public function testIsoDate($iso_date, $gap) {
+    $fd = new FacetsDateHandler();
+    $this->assertEquals($iso_date, $fd->isoDate(static::TIMESTAMP, $gap));
+  }
+
+  /**
+   * Tests for ::getNextDateGap.
+   */
+  public function testGetNextDateGap() {
+    $fd = new FacetsDateHandler();
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND);
+    $this->assertEquals($fd::FACETS_DATE_SECOND, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE);
+    $this->assertEquals($fd::FACETS_DATE_SECOND, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND, $fd::FACETS_DATE_MINUTE);
+    $this->assertEquals($fd::FACETS_DATE_MINUTE, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE, $fd::FACETS_DATE_MINUTE);
+    $this->assertEquals($fd::FACETS_DATE_MINUTE, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND, $fd::FACETS_DATE_HOUR);
+    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE, $fd::FACETS_DATE_HOUR);
+    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
+
+    $gap = $fd->getNextDateGap($fd::FACETS_DATE_HOUR, $fd::FACETS_DATE_HOUR);
+    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
+  }
+
+  /**
+   * Tests for ::getTimestampGap
+   */
+  public function testGetTimestampGap() {
+    $fd = new FacetsDateHandler();
+
+    // The best search gap between two dates must be a year.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 31536000);
+    $this->assertEquals($fd::FACETS_DATE_YEAR, $date_gap);
+
+    // The best search gap between two dates must be a month.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 86400 * 60);
+    $this->assertEquals($fd::FACETS_DATE_MONTH, $date_gap);
+
+    // The best search gap between two dates must be a day.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 86400);
+    $this->assertEquals($fd::FACETS_DATE_DAY, $date_gap);
+
+    // The best search gap between two dates must be an hour.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 3600);
+    $this->assertEquals($fd::FACETS_DATE_HOUR, $date_gap);
+
+    // The best search gap between two dates must be a minute.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 60);
+    $this->assertEquals($fd::FACETS_DATE_MINUTE, $date_gap);
+
+    // The best search gap between two dates must be a second.
+    $date_gap = $fd->getTimestampGap(static::TIMESTAMP, static::TIMESTAMP + 59);
+    $this->assertEquals($fd::FACETS_DATE_SECOND, $date_gap);
+  }
+
+  /**
+   * Tests for ::getDateGap method.
+   */
+  public function testGetDateGap() {
+    $fd = new FacetsDateHandler();
+
+    // Cannot convert to timestamp.
+    $this->assertFalse($fd->getDateGap(static::TIMESTAMP, static::TIMESTAMP));
+
+    // The min. gap is MONTH but the result is larger.
+    $this->assertEquals($fd::FACETS_DATE_YEAR, $fd->getDateGap('1983-03-03T20:43:04Z', '1987-11-26T20:43:04Z', $fd::FACETS_DATE_MONTH));
+
+    // The gap is YEAR.
+    $this->assertEquals($fd::FACETS_DATE_YEAR, $fd->getDateGap('1983-03-03T20:43:04Z', '1987-11-26T20:43:04Z'));
+
+    // The gap is MONTH.
+    $this->assertEquals($fd::FACETS_DATE_MONTH, $fd->getDateGap('1983-03-03T20:43:04Z', '1983-11-26T20:43:04Z'));
+
+    // The gap is DAY.
+    $this->assertEquals($fd::FACETS_DATE_DAY, $fd->getDateGap('1983-03-03T20:43:04Z', '1983-03-26T20:43:04Z'));
+
+    // The gap is HOUR.
+    $this->assertEquals($fd::FACETS_DATE_HOUR, $fd->getDateGap('1983-03-03T20:43:04Z', '1983-03-03T21:44:04Z'));
+
+    // The gap is MINUTE.
+    $this->assertEquals($fd::FACETS_DATE_MINUTE, $fd->getDateGap('1983-03-03T20:43:04Z', '1983-03-03T20:44:04Z'));
+
+    // The gap is SECOND.
+    $this->assertEquals($fd::FACETS_DATE_SECOND, $fd->getDateGap('1983-03-03T20:43:04Z', '1983-03-03T20:43:55Z'));
+  }
+
+  /**
+   * Tests for ::nextDateIncrement method.
+   *
+   * @dataProvider provideNextDateIncrementData
+   */
+  public function testNextDateIncrement($incremented_iso_date, $gap) {
+    $fd = new FacetsDateHandler();
+
+    $this->assertEquals($incremented_iso_date, $fd->getNextDateIncrement(static::ISO_DATE, $gap));
+  }
+
+  /**
+   * Tests for ::gapCompare method.
+   */
+  public function testGapCompare() {
+    $fd = new FacetsDateHandler();
+
+    // Timestamps are equals.
+    $this->assertEquals(0, $fd->gapCompare(static::TIMESTAMP, static::TIMESTAMP));
+
+    // Timestamps are equals.
+    $this->assertEquals(0, $fd->gapCompare($fd::FACETS_DATE_YEAR, $fd::FACETS_DATE_YEAR));
+
+    // gap1 is less than gap2
+    $this->assertEquals(-1, $fd->gapCompare($fd::FACETS_DATE_MONTH, $fd::FACETS_DATE_YEAR));
+
+    // gap1 is less than gap2
+    $this->assertEquals(1, $fd->gapCompare($fd::FACETS_DATE_MONTH, $fd::FACETS_DATE_DAY));
+  }
+
+  /**
+   * Returns a data provider for the ::testIsoDate().
+   *
+   * @return array
+   */
+  public function provideIsoDates() {
+    return [
+      ['1987-11-26T20:43:04Z', FacetsDateHandler::FACETS_DATE_SECOND],
+      ['1987-11-26T20:43:00Z', FacetsDateHandler::FACETS_DATE_MINUTE],
+      ['1987-11-26T20:00:00Z', FacetsDateHandler::FACETS_DATE_HOUR],
+      ['1987-11-26T00:00:00Z', FacetsDateHandler::FACETS_DATE_DAY],
+      ['1987-11-01T00:00:00Z', FacetsDateHandler::FACETS_DATE_MONTH],
+      ['1987-01-01T00:00:00Z', FacetsDateHandler::FACETS_DATE_YEAR],
+      ['1987-11-26T20:43:04Z', FacetsDateHandler::FACETS_DATE_ISO8601],
+    ];
+  }
+
+  /**
+   * Returns a data provider for the ::testNextDateIncrement().
+   *
+   * @return array
+   */
+  public function provideNextDateIncrementData() {
+    return [
+      ['1987-11-26T20:43:05Z', FacetsDateHandler::FACETS_DATE_SECOND],
+      ['1987-11-26T20:44:04Z', FacetsDateHandler::FACETS_DATE_MINUTE],
+      ['1987-11-26T21:43:04Z', FacetsDateHandler::FACETS_DATE_HOUR],
+      ['1987-11-27T20:43:04Z', FacetsDateHandler::FACETS_DATE_DAY],
+      ['1987-12-26T20:43:04Z', FacetsDateHandler::FACETS_DATE_MONTH],
+      ['1988-11-26T20:43:04Z', FacetsDateHandler::FACETS_DATE_YEAR],
+    ];
+  }
+
+}
+
diff --git a/tests/src/Unit/Utility/FacetsDateTest.php b/tests/src/Unit/Utility/FacetsDateTest.php
deleted file mode 100644
index 206f86d..0000000
--- a/tests/src/Unit/Utility/FacetsDateTest.php
+++ /dev/null
@@ -1,105 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Tests\facets\Unit\Utility\FacetsDateTest.
- */
-
-namespace Drupal\Tests\facets\Unit\Utility;
-
-use Drupal\facets\Utility\FacetsDate;
-use Drupal\Tests\UnitTestCase;
-
-/**
- * Unit test for the checkbox widget form.
- *
- * @group facets
- */
-class FacetsDateTest extends UnitTestCase {
-
-  /**
-   * Tests the isoDate method.
-   *
-   * @dataProvider provideIsoDates
-   */
-  public function testIsoDate($iso_date, $gap) {
-    $fd = new FacetsDate();
-    $this->assertEquals($iso_date, $fd->isoDate(564957784, $gap));
-  }
-
-  /**
-   * Tests for ::getNextDateGap.
-   */
-  public function testGetNextDateGap() {
-    $fd = new FacetsDate();
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND);
-    $this->assertEquals($fd::FACETS_DATE_SECOND, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE);
-    $this->assertEquals($fd::FACETS_DATE_SECOND, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND, $fd::FACETS_DATE_MINUTE);
-    $this->assertEquals($fd::FACETS_DATE_MINUTE, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE, $fd::FACETS_DATE_MINUTE);
-    $this->assertEquals($fd::FACETS_DATE_MINUTE, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_SECOND, $fd::FACETS_DATE_HOUR);
-    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_MINUTE, $fd::FACETS_DATE_HOUR);
-    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
-
-    $gap = $fd->getNextDateGap($fd::FACETS_DATE_HOUR, $fd::FACETS_DATE_HOUR);
-    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
-  }
-
-  /**
-   * Tests for ::getTimestampGap
-   */
-  public function testGetTimestampGap() {
-    $fd = new FacetsDate();
-    $gap = $fd->getTimestampGap(564957784, 651962584);
-    $this->assertEquals($fd::FACETS_DATE_YEAR, $gap);
-
-    $gap = $fd->getTimestampGap(564957784, 651962584, $fd::FACETS_DATE_SECOND);
-    $this->assertEquals($fd::FACETS_DATE_YEAR, $gap);
-
-    $gap = $fd->getTimestampGap(564957784, 564967784);
-    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
-
-    $gap = $fd->getTimestampGap(564957784, 564967784, $fd::FACETS_DATE_SECOND);
-    $this->assertEquals($fd::FACETS_DATE_HOUR, $gap);
-
-    $gap = $fd->getTimestampGap(564957784, 564967784, $fd::FACETS_DATE_MONTH);
-    $this->assertEquals($fd::FACETS_DATE_MONTH, $gap);
-  }
-
-  /**
-   * Tests for ::getDateGap.
-   */
-  public function testGetDateGap() {
-    $fd = new FacetsDate();
-    $gap = $fd->getDateGap('1987-11-26T20:43:04Z', '1990-08-29T20:43:04Z');
-    $this->assertEquals($fd::FACETS_DATE_YEAR, $gap);
-  }
-
-  /**
-   * Returns a data provider for the ::testIsoDate().
-   *
-   * @return array
-   */
-  public function provideIsoDates() {
-    return [
-      ['1987-11-26T20:43:04Z', FacetsDate::FACETS_DATE_SECOND],
-      ['1987-11-26T20:43:00Z', FacetsDate::FACETS_DATE_MINUTE],
-      ['1987-11-26T20:00:00Z', FacetsDate::FACETS_DATE_HOUR],
-      ['1987-11-26T00:00:00Z', FacetsDate::FACETS_DATE_DAY],
-      ['1987-11-01T00:00:00Z', FacetsDate::FACETS_DATE_MONTH],
-      ['1987-01-01T00:00:00Z', FacetsDate::FACETS_DATE_YEAR],
-      ['1987-11-26T20:43:04Z', FacetsDate::FACETS_DATE_ISO8601],
-    ];
-  }
-
-}