diff --git a/application/controllers/Calendar.php b/application/controllers/Calendar.php
new file mode 100644
index 00000000..4b995f82
--- /dev/null
+++ b/application/controllers/Calendar.php
@@ -0,0 +1,542 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     https://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        https://easyappointments.org
+ * @since       v1.5.0
+ * ---------------------------------------------------------------------------- */
+
+/**
+ * Calendar controller. 
+ * 
+ * Handles calendar related operations.
+ *
+ * @package Controllers 
+ */
+class Calendar extends EA_Controller {
+    /**
+     * @var array
+     */
+    protected $permissions;
+    
+    /**
+     * Calendar constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct(); 
+        
+        $this->load->model('appointments_model'); 
+        $this->load->model('customers_model'); 
+        $this->load->model('services_model'); 
+        $this->load->model('providers_model');
+
+        $this->load->library('google_sync');
+        $this->load->library('notifications');
+        $this->load->library('synchronization');
+        $this->load->library('timezones');
+
+        $role_slug = session('role_slug');
+
+        if ($role_slug)
+        {
+            $this->permissions = $this->roles_model->get_permissions_by_slug($role_slug);
+        }
+    }
+
+    /**
+     * Save appointment changes that are made from the backend calendar page.
+     */
+    public function ajax_save_appointment()
+    {
+        try
+        {
+            // Save customer changes to the database.
+            $customer_data = request('customer_data');
+
+            if ($customer_data)
+            {
+                $customer = json_decode($customer_data, TRUE);
+
+                $required_permissions = ( ! isset($customer['id']))
+                    ? $this->permissions[PRIV_CUSTOMERS]['add']
+                    : $this->permissions[PRIV_CUSTOMERS]['edit'];
+
+                if ($required_permissions == FALSE)
+                {
+                    throw new Exception('You do not have the required permissions for this task.');
+                }
+
+                $customer['id'] = $this->customers_model->save($customer);
+            }
+
+            // Save appointment changes to the database.
+            $appointment_data = request('appointment_data');
+
+            $manage_mode = ! empty($appointment_data['id']);
+
+            if ($appointment_data)
+            {
+                $appointment = json_decode($appointment_data, TRUE);
+
+                $required_permissions = ( ! isset($appointment['id']))
+                    ? $this->permissions[PRIV_APPOINTMENTS]['add']
+                    : $this->permissions[PRIV_APPOINTMENTS]['edit'];
+
+                if ($required_permissions == FALSE)
+                {
+                    throw new Exception('You do not have the required permissions for this task.');
+                }
+
+                // If the appointment does not contain the customer record id, then it means that is going to be
+                // inserted. 
+                if ( ! isset($appointment['id_users_customer']))
+                {
+                    $appointment['id_users_customer'] = $customer['id'] ?? $customer_data['id'];
+                }
+
+                $appointment['id'] = $this->appointments_model->save($appointment);
+            }
+
+            if (empty($appointment['id']))
+            {
+                throw new RuntimeException('The appointment ID is not available.');
+            }
+
+            $appointment = $this->appointments_model->find($appointment['id']);
+            $provider = $this->providers_model->find($appointment['id_users_provider']);
+            $customer = $this->customers_model->find($appointment['id_users_customer']);
+            $service = $this->services_model->find($appointment['id_services']);
+
+            $settings = [
+                'company_name' => setting('company_name'),
+                'company_link' => setting('company_link'),
+                'company_email' => setting('company_email'),
+                'date_format' => setting('date_format'),
+                'time_format' => setting('time_format')
+            ];
+
+            $this->synchronization->sync_appointment_saved($appointment, $service, $provider, $customer, $settings, $manage_mode);
+
+            $this->notifications->notify_appointment_saved($appointment, $service, $provider, $customer, $settings, $manage_mode);
+
+            json_response([
+                'success' => TRUE,
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Delete appointment from the database.
+     *
+     * This method deletes an existing appointment from the database. Once this action is finished it cannot be undone.
+     * Notification emails are send to both provider and customer and the delete action is executed to the Google
+     * Calendar account of the provider, if the "google_sync" setting is enabled.
+     */
+    public function ajax_delete_appointment()
+    {
+        try
+        {
+            if (cannot('delete', 'appointments'))
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $appointment_id = request('appointment_id');
+
+            if (empty($appointment_id))
+            {
+                throw new Exception('No appointment id provided.');
+            }
+
+            // Store appointment data for later use in this method.
+            $appointment = $this->appointments_model->find($appointment_id);
+            $provider = $this->providers_model->find($appointment['id_users_provider']);
+            $customer = $this->customers_model->find($appointment['id_users_customer']);
+            $service = $this->services_model->find($appointment['id_services']);
+
+            $settings = [
+                'company_name' => setting('company_name'),
+                'company_email' => setting('company_email'),
+                'company_link' => setting('company_link'),
+                'date_format' => setting('date_format'),
+                'time_format' => setting('time_format')
+            ];
+
+            // Delete appointment record from the database.
+            $this->appointments_model->delete($appointment_id);
+
+            $this->notifications->notify_appointment_deleted($appointment, $service, $provider, $customer, $settings);
+
+            $this->synchronization->sync_appointment_deleted($appointment, $provider);
+
+            json_response([
+                'success' => TRUE,
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Insert of update unavailable time period to database.
+     */
+    public function ajax_save_unavailable()
+    {
+        try
+        {
+            // Check privileges
+            $unavailable = json_decode(request('unavailable'), TRUE);
+
+            $required_permissions = ( ! isset($unavailable['id']))
+                ? $this->permissions[PRIV_APPOINTMENTS]['add']
+                : $this->permissions[PRIV_APPOINTMENTS]['edit'];
+
+            if ( ! $required_permissions)
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $provider = $this->providers_model->find($unavailable['id_users_provider']);
+
+            // Add appointment
+            $unavailable['id'] = $this->unavailabilities_model->save($unavailable);
+
+            $unavailable = $this->unavailabilities_model->find($unavailable['id']); // fetch all inserted data
+
+            // Google Sync
+            try
+            {
+                $google_sync = $this->providers_model->get_setting($unavailable['id_users_provider'], 'google_sync');
+
+                if ($google_sync)
+                {
+                    $google_token = json_decode($this->providers_model->get_setting($unavailable['id_users_provider'], 'google_token'));
+
+                    $this->google_sync->refresh_token($google_token->refresh_token);
+
+                    if ($unavailable['id_google_calendar'] == NULL)
+                    {
+                        $google_event = $this->google_sync->add_unavailable($provider, $unavailable);
+                        $unavailable['id_google_calendar'] = $google_event->id;
+                        $this->unavailabilities_model->save($unavailable);
+                    }
+                    else
+                    {
+                        $this->google_sync->update_unavailable($provider, $unavailable);
+                    }
+                }
+            }
+            catch (Throwable $e)
+            {
+                $warnings[] = $e;
+            }
+
+            json_response([
+                'success' => TRUE,
+                'warnings' => $warnings ?? []
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Delete an unavailable time period from database.
+     */
+    public function ajax_delete_unavailable()
+    {
+        try
+        {
+            if ($this->permissions[PRIV_APPOINTMENTS]['delete'] == FALSE)
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $unavailable_id = request('unavailable_id');
+
+            $unavailable = $this->appointments_model->find($unavailable_id);
+
+            $provider = $this->providers_model->find($unavailable['id_users_provider']);
+
+            $this->appointments_model->delete($unavailable['id']);
+
+            // Google Sync
+            try
+            {
+                $google_sync = $this->providers_model->get_setting($provider['id'], 'google_sync');
+
+                if ($google_sync == TRUE)
+                {
+                    $google_token = json_decode($this->providers_model->get_setting($provider['id'], 'google_token'));
+
+                    $this->google_sync->refresh_token($google_token->refresh_token);
+
+                    $this->google_sync->delete_unavailable($provider, $unavailable['id_google_calendar']);
+                }
+            }
+            catch (Throwable $e)
+            {
+                $warnings[] = $e;
+            }
+
+            json_response([
+                'success' => TRUE,
+                'warnings' => $warnings ?? []
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Insert of update working plan exceptions to database.
+     */
+    public function ajax_save_working_plan_exception()
+    {
+        try
+        {
+            $required_permissions = $this->permissions[PRIV_USERS]['edit'];
+
+            if ( ! $required_permissions)
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $date = request('date');
+
+            $working_plan_exception = request('working_plan_exception');
+
+            $provider_id = request('provider_id');
+
+            $this->providers_model->save_working_plan_exception($provider_id, $date, $working_plan_exception);
+
+            json_response([
+                'success' => TRUE,
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Delete a working plan exceptions time period to database.
+     */
+    public function ajax_delete_working_plan_exception()
+    {
+        try
+        {
+            $required_permissions = $this->permissions[PRIV_USERS]['edit'];
+
+            if ( ! $required_permissions)
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $date = request('date');
+
+            $provider_id = request('provider_id');
+
+            $this->providers_model->delete_working_plan_exception($provider_id, $date);
+
+            json_response([
+                'success' => TRUE
+            ]);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Get Calendar Events
+     *
+     * This method will return all the calendar events within a specified period.
+     */
+    public function ajax_get_calendar_events()
+    {
+        try
+        {
+            $start_date = request('startDate') . ' 00:00:00';
+
+            $end_date = request('endDate') . ' 23:59:59';
+
+            $response = [
+                'appointments' => $this->appointments_model->get([
+                    'is_unavailable' => FALSE,
+                    'start_datetime >=' => $start_date,
+                    'end_datetime <=' => $end_date
+                ]),
+                'unavailability_events' => $this->appointments_model->get([
+                    'is_unavailable' => TRUE,
+                    'start_datetime >=' => $start_date,
+                    'end_datetime <=' => $end_date
+                ])
+            ];
+
+            foreach ($response['appointments'] as &$appointment)
+            {
+                $appointment['provider'] = $this->providers_model->find($appointment['id_users_provider']);
+                $appointment['service'] = $this->services_model->find($appointment['id_services']);
+                $appointment['customer'] = $this->customers_model->find($appointment['id_users_customer']);
+            }
+
+            unset($appointment);
+
+            $user_id = session('user_id');
+
+            $role_slug = session('role_slug');
+
+            // If the current user is a provider he must only see his own appointments.
+            if ($role_slug === DB_SLUG_PROVIDER)
+            {
+                foreach ($response['appointments'] as $index => $appointment)
+                {
+                    if ((int)$appointment['id_users_provider'] !== (int)$user_id)
+                    {
+                        unset($response['appointments'][$index]);
+                    }
+                }
+
+                foreach ($response['unavailability_events'] as $index => $unavailability_event)
+                {
+                    if ((int)$unavailability_event['id_users_provider'] !== (int)$user_id)
+                    {
+                        unset($response['unavailability_events'][$index]);
+                    }
+                }
+            }
+
+            // If the current user is a secretary he must only see the appointments of his providers.
+            if ($role_slug === DB_SLUG_SECRETARY)
+            {
+                $providers = $this->secretaries_model->find($user_id)['providers'];
+
+                foreach ($response['appointments'] as $index => $appointment)
+                {
+                    if ( ! in_array((int)$appointment['id_users_provider'], $providers))
+                    {
+                        unset($response['appointments'][$index]);
+                    }
+                }
+
+                foreach ($response['unavailability_events'] as $index => $unavailability_event)
+                {
+                    if ( ! in_array((int)$unavailability_event['id_users_provider'], $providers))
+                    {
+                        unset($response['unavailability_events'][$index]);
+                    }
+                }
+            }
+
+            json_response($response);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+
+    /**
+     * Get the registered appointments for the given date period and record.
+     *
+     * This method returns the database appointments and unavailable periods for the user selected date period and
+     * record type (provider or service).
+     */
+    public function ajax_get_calendar_appointments()
+    {
+        try
+        {
+            if ($this->permissions[PRIV_APPOINTMENTS]['view'] == FALSE)
+            {
+                throw new Exception('You do not have the required permissions for this task.');
+            }
+
+            $filter_type = request('filter_type');
+
+            if ( ! $filter_type)
+            {
+                json_response([
+                    'appointments' => [],
+                    'unavailables' => []
+                ]);
+
+                return;
+            }
+
+            if ($filter_type == FILTER_TYPE_PROVIDER)
+            {
+                $where_id = 'id_users_provider';
+            }
+            else
+            {
+                $where_id = 'id_services';
+            }
+
+            // Get appointments
+            $record_id = $this->db->escape(request('record_id'));
+            $start_date = $this->db->escape(request('start_date'));
+            $end_date = $this->db->escape(date('Y-m-d', strtotime(request('end_date') . ' +1 day')));
+
+            $where_clause = $where_id . ' = ' . $record_id . '
+                AND ((start_datetime > ' . $start_date . ' AND start_datetime < ' . $end_date . ') 
+                or (end_datetime > ' . $start_date . ' AND end_datetime < ' . $end_date . ') 
+                or (start_datetime <= ' . $start_date . ' AND end_datetime >= ' . $end_date . ')) 
+                AND is_unavailable = 0
+            ';
+
+            $response['appointments'] = $this->appointments_model->get($where_clause);
+
+            foreach ($response['appointments'] as &$appointment)
+            {
+                $appointment['provider'] = $this->providers_model->find($appointment['id_users_provider']);
+                $appointment['service'] = $this->services_model->find($appointment['id_services']);
+                $appointment['customer'] = $this->customers_model->find($appointment['id_users_customer']);
+            }
+
+            // Get unavailable periods (only for provider).
+            $response['unavailables'] = [];
+
+            if ($filter_type == FILTER_TYPE_PROVIDER)
+            {
+                $where_clause = $where_id . ' = ' . $record_id . '
+                    AND ((start_datetime > ' . $start_date . ' AND start_datetime < ' . $end_date . ') 
+                    or (end_datetime > ' . $start_date . ' AND end_datetime < ' . $end_date . ') 
+                    or (start_datetime <= ' . $start_date . ' AND end_datetime >= ' . $end_date . ')) 
+                    AND is_unavailable = 1
+                ';
+
+                $response['unavailables'] = $this->appointments_model->get($where_clause);
+            }
+
+            foreach ($response['unavailables'] as &$unavailable)
+            {
+                $unavailable['provider'] = $this->providers_model->find($unavailable['id_users_provider']);
+            }
+
+            json_response($response);
+        }
+        catch (Throwable $e)
+        {
+            json_exception($e);
+        }
+    }
+}