diff --git a/reserve.inc b/reserve.inc
index 4fc9059..54e975d 100644
--- a/reserve.inc
+++ b/reserve.inc
@@ -25,11 +25,13 @@ function reserve_categories($ebundle = null) {
     $ids = array_filter($fconfig['categories']);
   }
   else {
-    $ids = Drupal::service('entity.query')
-      ->get('reserve_category')
-      ->condition('status', TRUE)
+    $query = \Drupal::service('entity_type.manager')->getStorage('reserve_category')->getQuery();
+    $ids = $query->condition('status', TRUE)->execute();
+    //$ids = Drupal::service('entity.query')
+      //->get('reserve_category')
+      //->condition('status', TRUE)
       //->sort('reserve_display_order', 'ASC')
-      ->execute();
+      //->execute();
   }
 
   $cats = \Drupal::entityTypeManager()->getStorage('reserve_category')->loadMultiple($ids);
@@ -59,9 +61,11 @@ function reserve_categories($ebundle = null) {
 function reserve_entities($ebundle) {
   $entity_type = ebundle_split($ebundle, 'type');
   $bundle = ebundle_split($ebundle, 'bundle');
-  $query = Drupal::service('entity.query')
-    ->get($entity_type)
-    ->condition('status', TRUE);
+  $query = \Drupal::service('entity_type.manager')->getStorage($entity_type)->getQuery();
+  $query->condition('status', TRUE);
+  //$query = Drupal::service('entity.query')
+  //  ->get($entity_type)
+  //  ->condition('status', TRUE);
 
   if ($entity_type != $bundle) {
     $query->condition('type', $bundle);
@@ -805,9 +809,8 @@ function reserve_valid_lengths($rid, $ebundle, $yyyy_mmdd, $time, $id = NULL, $a
       $start_time = $search_item['start_time'];
 
       $conflicts_found = false;
-
-      $query = Drupal::service('entity.query')
-        ->get('reserve_reservation')
+      $query = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+      //$query = Drupal::service('entity.query')
         ->condition('reservation_date', $date . '%', 'LIKE')
         ->condition('reservation_time', $start_time)
         ->condition('reservable_id', $rid)
@@ -936,8 +939,8 @@ function reserve_daily_max_exceeded($yyyy_mmdd) {
 
   $record_count = 0;
   if ($user->uid) {
-    $ids = \Drupal::service('entity.query')
-      ->get('reserve_reservation')
+    $ids = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+    //$ids = \Drupal::service('entity.query')
       ->condition('user_id', $user->id)
       ->condition('reservation_date', 'value', $yyyy_mmdd . '%', 'like')
       ->execute();
@@ -970,9 +973,9 @@ function reserve_user_reservations() {
   if ($user->id()) {
     $earliest_date = date('Y-m-d', strtotime(date('Y-m-d')));
     $latest_date = date('Y-m-d', strtotime("now +13 days"));
-
-    $ids = \Drupal::service('entity.query')
-      ->get('reserve_reservation')
+    $ids = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+    //$ids = \Drupal::service('entity.query')
+    //  ->get('reserve_reservation')
       ->condition('user_id', $user->id())
       ->condition('reservation_date', $earliest_date, '>=')
       ->condition('reservation_date', $latest_date, '<=')
@@ -1032,7 +1035,7 @@ function reserve_yyyymmdd($month, $day) {
  */
 function reserve_get_reserve_bundles() {
   $bundles = array();
-  $fieldmap = \Drupal::entityManager()->getFieldMap();
+  $fieldmap = \Drupal::service('entity_field.manager')->getFieldMap();
   foreach ($fieldmap as $entity_type => $typedef) {
     foreach ($typedef as $field) {
       if ($field['type'] == 'reserve_category') {
@@ -1050,7 +1053,7 @@ function reserve_get_reserve_bundles() {
  * OR specific field name if $ebundle is provided (e.g. node.room)
  */
 function reserve_category_fields($ebundle = NULL) {
-  $fieldmap = \Drupal::entityManager()->getFieldMap();
+  $fieldmap = \Drupal::service('entity_field.manager')->getFieldMap();
   $fields = [];
   foreach ($fieldmap as $entity_type => $typedef) {
     foreach ($typedef as $name => $field) {
diff --git a/reserve.info.yml b/reserve.info.yml
index b112d65..4868934 100644
--- a/reserve.info.yml
+++ b/reserve.info.yml
@@ -3,6 +3,7 @@ type: module
 description: Reservation system.
 core: 8.x
 package: Reserve
+core_version_requirement: ^8 || ^9
 dependencies:
   - drupal:views
   - drupal:options
diff --git a/reserve.series.inc b/reserve.series.inc
index ecdb5a5..4823d5d 100644
--- a/reserve.series.inc
+++ b/reserve.series.inc
@@ -85,12 +85,12 @@ function reserve_reserve_reservation_insert($entity) {
 
   // lets spit out some useful msgs
   // first clear the msg stating we just created the reservation entity
-  drupal_get_messages('status');
-  drupal_set_message(t('Your reservation series has been booked.'));
-  drupal_set_message($msg);
+  \Drupal::messenger()->addStatus('status');
+  \Drupal::messenger()->addStatus(t('Your reservation series has been booked.'));
+  \Drupal::messenger()->addStatus($msg);
   if (count($failed)) {
     $dates = Markup::create('<br>' . implode('<br>', $failed));
-    drupal_set_message(t('The following dates were not booked due to scheduling conflicts: %dates', array('%dates' => $dates)), 'warning');
+    \Drupal::messenger()->addWarning(t('The following dates were not booked due to scheduling conflicts: %dates', array('%dates' => $dates)));
   }
 }
 
@@ -126,8 +126,9 @@ function reserve_reserve_reservation_update($entity) {
   $private = $entity->reservation_private->getString();
 
   // grab all reservations in this series except the one being submitted
-  $ids = \Drupal::service('entity.query')
-    ->get('reserve_reservation')
+  $ids = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+  //$ids = \Drupal::service('entity.query')
+ //   ->get('reserve_reservation')
     ->condition('status', TRUE)
     ->condition('reservation_series_id', $sid)
     ->condition('id', $entity->id(), '!=')
@@ -156,10 +157,10 @@ function reserve_reserve_reservation_update($entity) {
   }
 
   // lets spit out some useful msgs
-  drupal_set_message(t('Your reservation series has been modified.'));
+  \Drupal::messenger()->addStatus(t('Your reservation series has been modified.'));
   if (count($failed)) {
     $dates = Markup::create('<br>' . implode('<br>', $failed));
-    drupal_set_message(t('NOTE: The following dates did not have their length changed due to scheduling conflicts: %dates', array('%dates' => $dates)), 'warning');
+    \Drupal::messenger()->addStatus(t('NOTE: The following dates did not have their length changed due to scheduling conflicts: %dates', array('%dates' => $dates)));
   }  
 }
 
@@ -179,8 +180,9 @@ function reserve_reserve_reservation_delete($entity) {
 function _reserve_series_delete($entity) {
   $sid = $entity->get('reservation_series_id')->getString();
   // grab all reservations in this series
-  $ids = \Drupal::service('entity.query')
-    ->get('reserve_reservation')
+  $ids = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+  //$ids = \Drupal::service('entity.query')
+  //  ->get('reserve_reservation')
     ->condition('reservation_series_id', $sid)
     ->execute();
   $results = \Drupal::entityTypeManager()->getStorage('reserve_reservation')->loadMultiple($ids);
@@ -188,5 +190,5 @@ function _reserve_series_delete($entity) {
     $result->delete();
   }
   $title = $entity->get('name')->getString();
-  drupal_set_message(t('The reservation series @title was deleted.', array('@title' => $title)));  
+  \Drupal::messenger()->addStatus(t('The reservation series @title was deleted.', array('@title' => $title)));  
 }
diff --git a/src/Controller/CalendarController.php b/src/Controller/CalendarController.php
index 1724719..9c6e460 100644
--- a/src/Controller/CalendarController.php
+++ b/src/Controller/CalendarController.php
@@ -57,7 +57,7 @@ class CalendarController extends ControllerBase {
 
     // if no Categories left; we should not bother with the rest of this
     if (!count($categories)) {
-      drupal_set_message(t('There are no configured Reserve Categories. Please contact the System Administrator'), 'warning');
+      \Drupal::messenger()->addWarning(t('There are no configured Reserve Categories. Please contact the System Administrator'));
       return '';
     }
 
@@ -171,8 +171,9 @@ class CalendarController extends ControllerBase {
     }
 
     $results = array();
-    $ids = \Drupal::service('entity.query')
-      ->get('reserve_reservation')
+    $ids = \Drupal::service('entity_type.manager')->getStorage('reserve_reservation')->getQuery()
+    //$ids = \Drupal::service('entity.query')
+    //  ->get('reserve_reservation')
       ->condition('status', TRUE)
       ->condition('reservation_date', $yyyy_mmdd . '%', 'like')
       ->condition('reservation_ebundle', $ebundle)
@@ -357,7 +358,8 @@ class CalendarController extends ControllerBase {
     $variables['#reserve_room_instructions_text'] = $config->get('reserve_instructions') ? $config->get('reserve_instructions') :
       t('To make a reservation, click on the desired time/day in the calendar below. You will be asked to login.');
     $variables['#arrow'] = base_path() . drupal_get_path('module', 'reserve') . '/images/arrow-icon.png';
-    $variables['#date'] = format_date(strtotime($month . ' ' . $xday . ', ' . $year), 'custom', 'l, F d, Y');
+    $variables['#date'] = \Drupal::service('date.formatter')->format(strtotime($month . ' ' . $xday . ', ' . $year), 'custom', 'l, F d, Y');
+    //$variables['#date'] = format_date(strtotime($month . ' ' . $xday . ', ' . $year), 'custom', 'l, F d, Y');
     $variables['#date_picker'] = \Drupal::formBuilder()->getForm('Drupal\reserve\Form\CalendarDatePicker');
 
     $field = reserve_category_fields($ebundle);
diff --git a/src/Controller/ReservePermissions.php b/src/Controller/ReservePermissions.php
index 5a23065..b2e14fe 100644
--- a/src/Controller/ReservePermissions.php
+++ b/src/Controller/ReservePermissions.php
@@ -4,7 +4,7 @@
 namespace Drupal\reserve\Controller;
 
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
-use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -13,19 +13,19 @@ class ReservePermissions implements ContainerInjectionInterface {
   use StringTranslationTrait;
 
   /**
-   * The entity manager.
+   * The entity type manager.
    *
-   * @var \Drupal\Core\Entity\EntityManagerInterface
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
    */
   protected $entityManager;
 
   /**
    * Constructs a TaxonomyViewsIntegratorPermissions instance.
    *
-   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_manager
    *   The entity manager.
    */
-  public function __construct(EntityManagerInterface $entity_manager) {
+  public function __construct(EntityTypeManagerInterface $entity_manager) {
     $this->entityManager = $entity_manager;
   }
 
@@ -33,7 +33,7 @@ class ReservePermissions implements ContainerInjectionInterface {
    * {@inheritdoc}
    */
   public static function create(ContainerInterface $container) {
-    return new static($container->get('entity.manager'));
+    return new static($container->get('entity_type.manager'));
   }
 
   /**
diff --git a/src/Form/CalendarDatePicker.php b/src/Form/CalendarDatePicker.php
index 9cd892b..0015cee 100644
--- a/src/Form/CalendarDatePicker.php
+++ b/src/Form/CalendarDatePicker.php
@@ -49,7 +49,7 @@ class CalendarDatePicker extends FormBase {
   public function submitForm(array &$form, FormStateInterface $form_state) {
     // Display result.
     foreach ($form_state->getValues() as $key => $value) {
-      drupal_set_message($key . ': ' . $value);
+      \Drupal::messenger()->addStatus($key . ': ' . $value);
     }
   }
 
diff --git a/src/Form/ReserveCategoryForm.php b/src/Form/ReserveCategoryForm.php
index 557c971..749bfaa 100644
--- a/src/Form/ReserveCategoryForm.php
+++ b/src/Form/ReserveCategoryForm.php
@@ -34,13 +34,13 @@ class ReserveCategoryForm extends ContentEntityForm {
 
     switch ($status) {
       case SAVED_NEW:
-        drupal_set_message($this->t('Created the %label Reservation Category.', [
+        \Drupal::messenger()->addStatus($this->t('Created the %label Reservation Category.', [
           '%label' => $entity->label(),
         ]));
         break;
 
       default:
-        drupal_set_message($this->t('Saved the %label Reservation Category.', [
+        \Drupal::messenger()->addStatus($this->t('Saved the %label Reservation Category.', [
           '%label' => $entity->label(),
         ]));
     }
diff --git a/src/Form/ReserveDailyHoursForm.php b/src/Form/ReserveDailyHoursForm.php
index 54e8e5f..a380586 100644
--- a/src/Form/ReserveDailyHoursForm.php
+++ b/src/Form/ReserveDailyHoursForm.php
@@ -245,6 +245,6 @@ class ReserveDailyHoursForm extends ConfigFormBase {
     $this->config('reserve.monthly_hours')
       ->set($yyyy_mm, $updated_mo_hours)
       ->save();
-    drupal_set_message($confirmation);
+    \Drupal::messenger()->addStatus($confirmation);
   }
 }
diff --git a/src/Form/ReserveDefaultHoursForm.php b/src/Form/ReserveDefaultHoursForm.php
index a539aa1..98b744c 100644
--- a/src/Form/ReserveDefaultHoursForm.php
+++ b/src/Form/ReserveDefaultHoursForm.php
@@ -296,13 +296,13 @@ class ReserveDefaultHoursForm extends ConfigFormBase {
     $this->config('reserve.default_hours')
       ->set('data', $default_hours)
       ->save();
-    drupal_set_message($confirmation);
+    \Drupal::messenger()->addStatus ($confirmation);
 
     // save updated monthly override hours
     $this->config('reserve.monthly_hours')
       ->set('data', $monthly_hours)
       ->save();
-    drupal_set_message(t('Daily overrides updated with new defaults.'));
+    \Drupal::messenger()->addStatus(t('Daily overrides updated with new defaults.'));
   }
 
 }
diff --git a/src/Form/ReserveReservationForm.php b/src/Form/ReserveReservationForm.php
index 7194384..e137cbd 100644
--- a/src/Form/ReserveReservationForm.php
+++ b/src/Form/ReserveReservationForm.php
@@ -34,13 +34,13 @@ class ReserveReservationForm extends ContentEntityForm {
 
     switch ($status) {
       case SAVED_NEW:
-        drupal_set_message($this->t('Created the %label Reservation.', [
+       \Drupal::messenger()->addStatus ($this->t('Created the %label Reservation.', [
           '%label' => $entity->label(),
         ]));
         break;
 
       default:
-        drupal_set_message($this->t('Saved the %label Reservation.', [
+        \Drupal::messenger()->addStatus($this->t('Saved the %label Reservation.', [
           '%label' => $entity->label(),
         ]));
     }
diff --git a/src/Form/ReserveSettingsForm.php b/src/Form/ReserveSettingsForm.php
index ce3242e..701523b 100644
--- a/src/Form/ReserveSettingsForm.php
+++ b/src/Form/ReserveSettingsForm.php
@@ -177,7 +177,7 @@ class ReserveSettingsForm extends ConfigFormBase {
       $this->config('reserve.settings')->set($key, $value);
     }
     $this->config('reserve.settings')->save();
-    drupal_set_message(RESERVE_SAVE_CONFIRMATION_MSG);
+    \Drupal::messenger()->addStatus(RESERVE_SAVE_CONFIRMATION_MSG);
   }
 
 }
diff --git a/src/ReserveCategoryListBuilder.php b/src/ReserveCategoryListBuilder.php
index 4a8a917..7e5d8bf 100644
--- a/src/ReserveCategoryListBuilder.php
+++ b/src/ReserveCategoryListBuilder.php
@@ -6,6 +6,7 @@ use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityListBuilder;
 use Drupal\Core\Routing\LinkGeneratorTrait;
 use Drupal\Core\Url;
+use Drupal\Core\Link;
 
 /**
  * Defines a class to build a listing of reservation categories.
@@ -14,7 +15,6 @@ use Drupal\Core\Url;
  */
 class ReserveCategoryListBuilder extends EntityListBuilder {
 
-  use LinkGeneratorTrait;
 
   /**
    * {@inheritdoc}
@@ -31,14 +31,14 @@ class ReserveCategoryListBuilder extends EntityListBuilder {
   public function buildRow(EntityInterface $entity) {
     /* @var $entity \Drupal\reserve\Entity\ReserveCategory */
     $row['id'] = $entity->id();
-    $row['name'] = $this->l(
+    $row['name'] = Link::fromTextAndUrl(
       $entity->label(),
       new Url(
         'entity.reserve_category.edit_form', array(
           'reserve_category' => $entity->id(),
         )
       )
-    );
+    )->toString();
     return $row + parent::buildRow($entity);
   }
 
diff --git a/src/ReserveReservationListBuilder.php b/src/ReserveReservationListBuilder.php
index b2af230..68a91d7 100644
--- a/src/ReserveReservationListBuilder.php
+++ b/src/ReserveReservationListBuilder.php
@@ -6,6 +6,7 @@ use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityListBuilder;
 use Drupal\Core\Routing\LinkGeneratorTrait;
 use Drupal\Core\Url;
+use Drupal\Core\Link;
 
 /**
  * Defines a class to build a listing of reservations.
@@ -14,7 +15,6 @@ use Drupal\Core\Url;
  */
 class ReserveReservationListBuilder extends EntityListBuilder {
 
-  use LinkGeneratorTrait;
 
   /**
    * {@inheritdoc}
@@ -31,14 +31,14 @@ class ReserveReservationListBuilder extends EntityListBuilder {
   public function buildRow(EntityInterface $entity) {
     /* @var $entity \Drupal\reserve\Entity\ReserveReservation */
     $row['id'] = $entity->id();
-    $row['name'] = $this->l(
+    $row['name'] = Link::fromTextAndUrl(
       $entity->label(),
       new Url(
         'entity.reserve_reservation.edit_form', array(
           'reserve_reservation' => $entity->id(),
         )
       )
-    );
+    )->toString();
     return $row + parent::buildRow($entity);
   }