diff --git a/addons/calendar/__manifest__.py b/addons/calendar/__manifest__.py
index 2b1340d36e2..20466920cd4 100644
--- a/addons/calendar/__manifest__.py
+++ b/addons/calendar/__manifest__.py
@@ -26,9 +26,9 @@ If you need to manage your meetings, you should install the CRM module.
         'security/ir.model.access.csv',
         'security/calendar_security.xml',
         'data/calendar_cron.xml',
+        'data/mail_template_data.xml',
         'data/calendar_data.xml',
         'data/mail_data_various.xml',
-        'data/mail_template_data.xml',
         'views/mail_activity_views.xml',
         'views/calendar_templates.xml',
         'views/calendar_views.xml',
diff --git a/addons/calendar/data/calendar_data.xml b/addons/calendar/data/calendar_data.xml
index 124cd1abfb3..037117e6852 100644
--- a/addons/calendar/data/calendar_data.xml
+++ b/addons/calendar/data/calendar_data.xml
@@ -36,12 +36,14 @@
             <field name="duration" eval="3" />
             <field name="interval">hours</field>
             <field name="alarm_type">email</field>
+            <field name="mail_template_id" ref="calendar.calendar_template_meeting_reminder"/>
         </record>
         <record id="alarm_mail_2" model="calendar.alarm">
             <field name="name">Email - 6 Hours</field>
             <field name="duration" eval="6" />
             <field name="interval">hours</field>
             <field name="alarm_type">email</field>
+            <field name="mail_template_id" ref="calendar.calendar_template_meeting_reminder"/>
         </record>
     </data>
-</odoo>
\ No newline at end of file
+</odoo>
diff --git a/addons/calendar/models/calendar_alarm.py b/addons/calendar/models/calendar_alarm.py
index 7fcb5ba0aad..2ea15fd017b 100644
--- a/addons/calendar/models/calendar_alarm.py
+++ b/addons/calendar/models/calendar_alarm.py
@@ -21,6 +21,12 @@ class Alarm(models.Model):
         'Duration in minutes', store=True,
         search='_search_duration_minutes', compute='_compute_duration_minutes',
         help="Duration in minutes")
+    mail_template_id = fields.Many2one(
+        'mail.template', string="Email Template",
+        domain=[('model', 'in', ['calendar.attendee'])],
+        compute='_compute_mail_template_id', readonly=False, store=True,
+        help="Template used to render mail reminder content.")
+    body = fields.Text("Additional Message", help="Additional message that would be sent with the notification for the reminder")
 
     @api.depends('interval', 'duration')
     def _compute_duration_minutes(self):
@@ -34,6 +40,14 @@ class Alarm(models.Model):
             else:
                 alarm.duration_minutes = 0
 
+    @api.depends('alarm_type', 'mail_template_id')
+    def _compute_mail_template_id(self):
+        for alarm in self:
+            if alarm.alarm_type == 'email' and not alarm.mail_template_id:
+                alarm.mail_template_id = self.env['ir.model.data'].xmlid_to_res_id('calendar.calendar_template_meeting_reminder')
+            elif alarm.alarm_type != 'email' or not alarm.mail_template_id:
+                alarm.mail_template_id = False
+
     def _search_duration_minutes(self, operator, value):
         return [
             '|', '|',
diff --git a/addons/calendar/models/calendar_alarm_manager.py b/addons/calendar/models/calendar_alarm_manager.py
index 45af762a7a4..7babd72d105 100644
--- a/addons/calendar/models/calendar_alarm_manager.py
+++ b/addons/calendar/models/calendar_alarm_manager.py
@@ -5,6 +5,7 @@ import logging
 from datetime import timedelta
 
 from odoo import api, fields, models
+from odoo.tools import plaintext2html
 
 _logger = logging.getLogger(__name__)
 
@@ -135,7 +136,7 @@ class AlarmManager(models.AbstractModel):
             })
         return result
 
-    def _get_events_to_notify(self, ttype):
+    def _get_events_by_alarm_to_notify(self, alarm_type):
         """
         Get the events with an alarm of the given type between the cron
         last call and now.
@@ -146,7 +147,7 @@ class AlarmManager(models.AbstractModel):
         already.
         """
         self.env.cr.execute('''
-            SELECT "event"."id"
+            SELECT "alarm"."id", "event"."id"
               FROM "calendar_event" AS "event"
               JOIN "calendar_alarm_calendar_event_rel" AS "event_alarm_rel"
                 ON "event"."id" = "event_alarm_rel"."calendar_event_id"
@@ -157,20 +158,33 @@ class AlarmManager(models.AbstractModel):
                AND "event"."active"
                AND "event"."start" - CAST("alarm"."duration" || ' ' || "alarm"."interval" AS Interval) >= %s
                AND "event"."start" - CAST("alarm"."duration" || ' ' || "alarm"."interval" AS Interval) < now() at time zone 'utc'
-             )''', [ttype, self.env.context['lastcall']])
+             )''', [alarm_type, self.env.context['lastcall']])
 
-        ids = [row[0] for row in self.env.cr.fetchall()]
-        return self.env['calendar.event'].browse(ids)
+        events_by_alarm = {}
+        for alarm_id, event_id in self.env.cr.fetchall():
+            events_by_alarm.setdefault(alarm_id, list()).append(event_id)
+        return events_by_alarm
 
     @api.model
     def _send_reminder(self):
         # Executed via cron
-        events = self._get_events_to_notify('email')
+        events_by_alarm = self._get_events_by_alarm_to_notify('email')
+        if not events_by_alarm:
+            return
+
+        event_ids = list(set(event_id for event_ids in events_by_alarm.values() for event_id in event_ids))
+        events = self.env['calendar.event'].browse(event_ids)
         attendees = events.attendee_ids.filtered(lambda a: a.state != 'declined')
-        attendees.with_context(calendar_template_ignore_recurrence=True)._send_mail_to_attendees(
-            self.env.ref('calendar.calendar_template_meeting_reminder', raise_if_not_found=False),
-            force_send=True,
-        )
+        alarms = self.env['calendar.alarm'].browse(events_by_alarm.keys())
+        for alarm in alarms:
+            alarm_attendees = attendees.filtered(lambda attendee: attendee.event_id.id in events_by_alarm[alarm.id])
+            alarm_attendees.with_context(
+                mail_notify_force_send=True,
+                calendar_template_ignore_recurrence=True
+            )._send_mail_to_attendees(
+                alarm.mail_template_id,
+                force_send=True
+            )
 
     @api.model
     def get_next_notif(self):
@@ -198,6 +212,8 @@ class AlarmManager(models.AbstractModel):
 
         if alarm.alarm_type == 'notification':
             message = meeting.display_time
+            if alarm.body:
+                message += '<p>%s</p>' % plaintext2html(alarm.body)
 
             delta = alert['notify_at'] - fields.Datetime.now()
             delta = delta.seconds + delta.days * 3600 * 24
diff --git a/addons/calendar/views/calendar_views.xml b/addons/calendar/views/calendar_views.xml
index 545dd732253..0ec4a0bac11 100644
--- a/addons/calendar/views/calendar_views.xml
+++ b/addons/calendar/views/calendar_views.xml
@@ -23,7 +23,7 @@
         <field name="name">calendar.alarm.tree</field>
         <field name="model">calendar.alarm</field>
         <field name="arch" type="xml">
-            <tree string="Calendar Alarm" sample="1" editable="bottom">
+            <tree string="Calendar Alarm" sample="1">
                 <field name="name" invisible="1"/>
                 <field name="alarm_type"/>
                 <field name="duration"/>
@@ -33,23 +33,32 @@
     </record>
 
     <record id="calendar_alarm_view_form" model="ir.ui.view">
-            <field name="name">calendar.alarm.form</field>
-            <field name="model">calendar.alarm</field>
-            <field name="arch" type="xml">
-                <form string="Calendar Alarm">
-                 <group>
+        <field name="name">calendar.alarm.form</field>
+        <field name="model">calendar.alarm</field>
+        <field name="arch" type="xml">
+            <form string="Calendar Alarm">
+                <sheet>
                     <group>
-                        <field name="name" invisible="1"/>
-                        <field name="alarm_type"/>
+                        <group>
+                            <field name="name" invisible="1"/>
+                            <field name="alarm_type"/>
+                        </group>
+                        <group>
+                            <label for="duration"/>
+                            <div class="o_row">
+                                <field name="duration"/>
+                                <field name="interval"/>
+                            </div>
+                        </group>
+                        <group attrs="{'invisible': [('alarm_type','=','notification')]}">
+                            <field name="mail_template_id" attrs="{'invisible': [('alarm_type','!=','email')], 'required': [('alarm_type', '=', 'email')]}"
+                                context="{'default_model': 'calendar.event'}"/>
+                        </group>
                     </group>
-                    <group>
-                        <label for="duration"/>
-                        <div class="o_row">
-                            <field name="duration"/>
-                            <field name="interval"/>
-                        </div>
+                    <group attrs="{'invisible': [('alarm_type','!=','notification')]}">
+                        <field name="body"/>
                     </group>
-                </group>
+                </sheet>
             </form>
         </field>
     </record>
@@ -57,6 +66,7 @@
     <record id="action_calendar_alarm" model="ir.actions.act_window">
         <field name="name">Calendar Alarm</field>
         <field name="res_model">calendar.alarm</field>
+        <field name="view_mode">tree,form</field>
         <field name="view_id" ref="view_calendar_alarm_tree"/>
     </record>
 
diff --git a/addons/calendar_sms/__manifest__.py b/addons/calendar_sms/__manifest__.py
index efcff3de620..5799c4c2432 100644
--- a/addons/calendar_sms/__manifest__.py
+++ b/addons/calendar_sms/__manifest__.py
@@ -3,6 +3,7 @@
 
 {
     'name': "Calendar - SMS",
+    'version': "1.1",
     'summary': 'Send text messages as event reminders',
     'description': "Send text messages as event reminders",
     'category': 'Hidden',
diff --git a/addons/calendar_sms/models/calendar_alarm.py b/addons/calendar_sms/models/calendar_alarm.py
index 3c83268bba7..d69c1b17406 100644
--- a/addons/calendar_sms/models/calendar_alarm.py
+++ b/addons/calendar_sms/models/calendar_alarm.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import fields, models
+from odoo import api, fields, models
 
 
 class CalendarAlarm(models.Model):
@@ -10,3 +10,16 @@ class CalendarAlarm(models.Model):
     alarm_type = fields.Selection(selection_add=[
         ('sms', 'SMS Text Message')
     ], ondelete={'sms': 'set default'})
+    sms_template_id = fields.Many2one(
+        'sms.template', string="SMS Template",
+        domain=[('model', 'in', ['calendar.event'])],
+        compute='_compute_sms_template_id', readonly=False, store=True,
+        help="Template used to render SMS reminder content.")
+
+    @api.depends('alarm_type', 'mail_template_id')
+    def _compute_sms_template_id(self):
+        for alarm in self:
+            if alarm.alarm_type == 'sms' and not alarm.sms_template_id:
+                alarm.sms_template_id = self.env['ir.model.data'].xmlid_to_res_id('calendar_sms.sms_template_data_calendar_reminder')
+            elif alarm.alarm_type != 'sms' or not alarm.sms_template_id:
+                alarm.sms_template_id = False
diff --git a/addons/calendar_sms/models/calendar_alarm_manager.py b/addons/calendar_sms/models/calendar_alarm_manager.py
index 8857c3c7607..bd2f4418c70 100644
--- a/addons/calendar_sms/models/calendar_alarm_manager.py
+++ b/addons/calendar_sms/models/calendar_alarm_manager.py
@@ -12,4 +12,13 @@ class AlarmManager(models.AbstractModel):
         """ Cron method, overridden here to send SMS reminders as well
         """
         super()._send_reminder()
-        self._get_events_to_notify(ttype='sms')._do_sms_reminder()
+        alarms_by_event = self._get_events_by_alarm_to_notify(ttype='sms')
+        if not alarms_by_event:
+            return
+
+        events = self.env['calendar.event'].browse(list(alarms_by_event.keys()))
+        attendees = events.attendee_ids.filtered(lambda a: a.state != 'declined')
+        for event_id in alarms_by_event.keys():
+            event_alarms = attendees.event_id.alarm_ids.filtered(lambda alarm: alarm.id in alarms_by_event.get(event_id, []))
+            for alarm in event_alarms:
+                events.browse(event_id)._do_sms_reminder(alarm)
diff --git a/addons/calendar_sms/models/calendar_event.py b/addons/calendar_sms/models/calendar_event.py
index 172c209c20d..deaca1e0dfb 100644
--- a/addons/calendar_sms/models/calendar_event.py
+++ b/addons/calendar_sms/models/calendar_event.py
@@ -13,11 +13,11 @@ class CalendarEvent(models.Model):
         """
         return self.mapped('attendee_ids').filtered(lambda att: att.state != 'declined').mapped('partner_id')
 
-    def _do_sms_reminder(self):
+    def _do_sms_reminder(self, alarm):
         """ Send an SMS text reminder to attendees that haven't declined the event """
         for event in self:
             event._message_sms_with_template(
-                template_xmlid='calendar_sms.sms_template_data_calendar_reminder',
+                template=alarm.sms_template_id,
                 template_fallback=_("Event reminder: %(name)s, %(time)s.", name=event.name, time=event.display_time),
                 partner_ids=self._sms_get_default_partners().ids,
                 put_in_queue=False
diff --git a/addons/calendar_sms/views/calendar_views.xml b/addons/calendar_sms/views/calendar_views.xml
index ea7def35501..f5d8eda5284 100644
--- a/addons/calendar_sms/views/calendar_views.xml
+++ b/addons/calendar_sms/views/calendar_views.xml
@@ -1,6 +1,18 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <odoo>
 
+    <record id="calendar_alarm_view_form" model="ir.ui.view">
+        <field name="name">calendar.alarm.view.form.inherit.calendar.sms</field>
+        <field name="model">calendar.alarm</field>
+        <field name="inherit_id" ref="calendar.calendar_alarm_view_form"/>
+        <field name="arch" type="xml">
+            <xpath expr="//field[@name='mail_template_id']" position="after">
+                <field name="sms_template_id" attrs="{'invisible': [('alarm_type','!=','sms')], 'required': [('alarm_type', '=', 'sms')]}"
+                    context="{'default_model': 'calendar.event'}"/>
+            </xpath>
+        </field>
+    </record>
+
     <!-- Add action entry in the Action Menu for Events -->
     <record id="calendar_event_act_window_sms_composer_single" model="ir.actions.act_window">
         <field name="name">Send SMS</field>
diff --git a/addons/hr_holidays/tests/test_company_leave.py b/addons/hr_holidays/tests/test_company_leave.py
index 81d20fe8f06..31d3b9cf38b 100644
--- a/addons/hr_holidays/tests/test_company_leave.py
+++ b/addons/hr_holidays/tests/test_company_leave.py
@@ -313,7 +313,7 @@ class TestCompanyLeave(TransactionCase):
         })
         company_leave._compute_date_from_to()
 
-        with self.assertQueryCount(__system__=737, admin=865):
+        with self.assertQueryCount(__system__=739, admin=865):
             # Original query count: 1987
             # Without tracking/activity context keys: 5154
             company_leave.action_validate()
diff --git a/addons/hr_work_entry_holidays/tests/test_performance.py b/addons/hr_work_entry_holidays/tests/test_performance.py
index cad64988199..cd823539586 100644
--- a/addons/hr_work_entry_holidays/tests/test_performance.py
+++ b/addons/hr_work_entry_holidays/tests/test_performance.py
@@ -31,7 +31,7 @@ class TestWorkEntryHolidaysPerformance(TestWorkEntryHolidaysBase):
         self.richard_emp.generate_work_entries(date(2018, 1, 1), date(2018, 1, 2))
         leave = self.create_leave(datetime(2018, 1, 1, 7, 0), datetime(2018, 1, 1, 18, 0))
 
-        with self.assertQueryCount(__system__=91, admin=99):
+        with self.assertQueryCount(__system__=92, admin=99):
             leave.action_validate()
         leave.action_refuse()