diff --git a/application/models/Admins_model.php b/application/models/Admins_model.php
index 37b5a540..83a644d6 100644
--- a/application/models/Admins_model.php
+++ b/application/models/Admins_model.php
@@ -22,6 +22,14 @@
  * @package Models
  */
 class Admins_Model extends CI_Model {
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('general');
+        $this->load->helper('data_validation');
+    }
+
     /**
      * Add (insert or update) an admin user record into database.
      *
@@ -63,8 +71,6 @@ class Admins_Model extends CI_Model {
      */
     public function validate($admin)
     {
-        $this->load->helper('data_validation');
-
         // If a record id is provided then check whether the record exists in the database.
         if (isset($admin['id']))
         {
@@ -227,8 +233,6 @@ class Admins_Model extends CI_Model {
      */
     protected function insert($admin)
     {
-        $this->load->helper('general');
-
         $admin['id_roles'] = $this->get_admin_role_id();
         $settings = $admin['settings'];
         unset($admin['settings']);
@@ -278,8 +282,6 @@ class Admins_Model extends CI_Model {
      */
     protected function update($admin)
     {
-        $this->load->helper('general');
-
         $settings = $admin['settings'];
         unset($admin['settings']);
         $settings['id_users'] = $admin['id'];
diff --git a/application/models/Appointments_model.php b/application/models/Appointments_model.php
index 5f86f8c5..8b49cde5 100644
--- a/application/models/Appointments_model.php
+++ b/application/models/Appointments_model.php
@@ -20,6 +20,18 @@
  * @package Models
  */
 class Appointments_Model extends CI_Model {
+    /**
+     * Appointments_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('data_validation');
+
+        $this->load->library('timezones');
+    }
+
     /**
      * Add an appointment record to the database.
      *
@@ -61,8 +73,6 @@ class Appointments_Model extends CI_Model {
      */
     public function validate($appointment)
     {
-        $this->load->helper('data_validation');
-
         // If a appointment id is given, check whether the record exists in the database.
         if (isset($appointment['id']))
         {
@@ -310,8 +320,6 @@ class Appointments_Model extends CI_Model {
 
         $appointment = $this->db->get_where('appointments', ['id' => $appointment_id])->row_array();
 
-        $this->load->library('timezones');
-
         $appointment = $this->timezones->convert_event_timezone($appointment);
 
         return $appointment;
@@ -356,8 +364,6 @@ class Appointments_Model extends CI_Model {
             throw new Exception('The given field name does not exist in the database: ' . $field_name);
         }
 
-        $this->load->library('timezones');
-
         $row_data = $this->timezones->convert_event_timezone($row_data);
 
         return $row_data[$field_name];
@@ -393,8 +399,6 @@ class Appointments_Model extends CI_Model {
 
         $appointments = $this->db->get('appointments', $limit, $offset)->result_array();
 
-        $this->load->library('timezones');
-
         foreach ($appointments as &$appointment)
         {
             $appointment = $this->timezones->convert_event_timezone($appointment);
diff --git a/application/models/Customers_model.php b/application/models/Customers_model.php
index d11fa165..94409bed 100644
--- a/application/models/Customers_model.php
+++ b/application/models/Customers_model.php
@@ -20,6 +20,16 @@
  * @package Models
  */
 class Customers_Model extends CI_Model {
+    /**
+     * Customers_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('data_validation');
+    }
+
     /**
      * Add a customer record to the database.
      *
@@ -68,10 +78,7 @@ class Customers_Model extends CI_Model {
      */
     public function validate($customer)
     {
-        $this->load->helper('data_validation');
-
-        // If a customer id is provided, check whether the record
-        // exist in the database.
+        // If a customer id is provided, check whether the record exist in the database.
         if (isset($customer['id']))
         {
             $num_rows = $this->db->get_where('users',
diff --git a/application/models/Providers_model.php b/application/models/Providers_model.php
index cf354cd8..bac0b4b5 100755
--- a/application/models/Providers_model.php
+++ b/application/models/Providers_model.php
@@ -22,6 +22,17 @@
  * @package Models
  */
 class Providers_Model extends CI_Model {
+    /**
+     * Providers_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('data_validation');
+        $this->load->helper('general');
+    }
+
     /**
      * Add (insert - update) a service provider record.
      *
@@ -66,7 +77,6 @@ class Providers_Model extends CI_Model {
      */
     public function validate($provider)
     {
-        $this->load->helper('data_validation');
 
         // If a provider id is present, check whether the record exist in the database.
         if (isset($provider['id']))
@@ -254,7 +264,6 @@ class Providers_Model extends CI_Model {
      */
     protected function insert($provider)
     {
-        $this->load->helper('general');
 
         // Get provider role id.
         $provider['id_roles'] = $this->get_providers_role_id();
@@ -394,8 +403,6 @@ class Providers_Model extends CI_Model {
      */
     protected function update($provider)
     {
-        $this->load->helper('general');
-
         // Store service and settings (must not be present on the $provider array).
         $services = $provider['services'];
         unset($provider['services']);
diff --git a/application/models/Secretaries_model.php b/application/models/Secretaries_model.php
index 861a20a0..d08f7891 100644
--- a/application/models/Secretaries_model.php
+++ b/application/models/Secretaries_model.php
@@ -22,6 +22,17 @@
  * @package Models
  */
 class Secretaries_Model extends CI_Model {
+    /**
+     * Secretaries_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('general');
+        $this->load->helper('data_validation');
+    }
+
     /**
      * Add (insert or update) a secretary user record into database.
      *
@@ -63,8 +74,6 @@ class Secretaries_Model extends CI_Model {
      */
     public function validate($secretary)
     {
-        $this->load->helper('data_validation');
-
         // If a record id is provided then check whether the record exists in the database.
         if (isset($secretary['id']))
         {
@@ -233,8 +242,6 @@ class Secretaries_Model extends CI_Model {
      */
     protected function insert($secretary)
     {
-        $this->load->helper('general');
-
         $providers = $secretary['providers'];
         unset($secretary['providers']);
         $settings = $secretary['settings'];
@@ -358,8 +365,6 @@ class Secretaries_Model extends CI_Model {
      */
     protected function update($secretary)
     {
-        $this->load->helper('general');
-
         $providers = $secretary['providers'];
         unset($secretary['providers']);
         $settings = $secretary['settings'];
diff --git a/application/models/Services_model.php b/application/models/Services_model.php
index df6d101a..b6767493 100644
--- a/application/models/Services_model.php
+++ b/application/models/Services_model.php
@@ -20,6 +20,16 @@
  * @package Models
  */
 class Services_Model extends CI_Model {
+    /**
+     * Services_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->helper('data_validation');
+    }
+
     /**
      * Add (insert or update) a service record on the database
      *
@@ -55,14 +65,11 @@ class Services_Model extends CI_Model {
      */
     public function validate($service)
     {
-        $this->load->helper('data_validation');
-
-        // If record id is provided we need to check whether the record exists
-        // in the database.
+        // If record id is provided we need to check whether the record exists in the database.
         if (isset($service['id']))
         {
-            $num_rows = $this->db->get_where('services', ['id' => $service['id']])
-                ->num_rows();
+            $num_rows = $this->db->get_where('services', ['id' => $service['id']])->num_rows();
+
             if ($num_rows == 0)
             {
                 throw new Exception('Provided service id does not exist in the database.');
diff --git a/application/models/User_model.php b/application/models/User_model.php
index 417734aa..64db2564 100644
--- a/application/models/User_model.php
+++ b/application/models/User_model.php
@@ -22,6 +22,19 @@
  * @package Models
  */
 class User_Model extends CI_Model {
+    /**
+     * User_Model constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->library('timezones');
+
+        $this->load->helper('general');
+        $this->load->helper('string');
+    }
+
     /**
      * Returns the user from the database for the "settings" page.
      *
@@ -53,7 +66,6 @@ class User_Model extends CI_Model {
         // Prepare user password (hash).
         if (isset($user_settings['password']))
         {
-            $this->load->helper('general');
             $salt = $this->db->get_where('user_settings', ['id_users' => $user['id']])->row()->salt;
             $user_settings['password'] = hash_password($salt, $user_settings['password']);
         }
@@ -81,7 +93,6 @@ class User_Model extends CI_Model {
      */
     public function check_login($username, $password)
     {
-        $this->load->helper('general');
         $salt = $this->get_salt($username);
         $password = hash_password($salt, $password);
 
@@ -109,8 +120,6 @@ class User_Model extends CI_Model {
             return NULL;
         }
 
-        $this->load->library('timezones');
-
         $default_timezone = $this->timezones->get_default_timezone();
 
         return [
@@ -167,9 +176,6 @@ class User_Model extends CI_Model {
      */
     public function regenerate_password($username, $email)
     {
-        $this->load->helper('general');
-        $this->load->helper('string');
-
         $result = $this->db
             ->select('users.id')
             ->from('users')