diff --git a/addons/base_calendar/base_calendar_view.xml b/addons/base_calendar/base_calendar_view.xml
index fa073938a37..eeaa71b3eed 100644
--- a/addons/base_calendar/base_calendar_view.xml
+++ b/addons/base_calendar/base_calendar_view.xml
@@ -10,20 +10,10 @@
             <field name="arch" type="xml">
                 <form string="Invitation details" version="7.0">
                     <header>
-                        <button name="do_tentative"
-                            states="needs-action,declined,accepted"
-                            string="Uncertain" type="object"/>
-                        <button name="do_accept" string="Accept"
-                            states="needs-action,tentative,declined"
-                            type="object" />
-                        <button
-                            name="%(base_calendar.action_view_calendar_invite_attendee_wizard)d"
-                            string="Delegate" type="action"
-                            states="needs-action,tentative,declined,accepted"
-                            context="{'model' : 'calendar.attendee', 'attendee_field' : 'child_ids'}" />
-                        <button name="do_decline" string="Decline"
-                            states="needs-action,tentative,accepted"
-                            type="object" />
+                        <button name="do_tentative" states="needs-action,declined,accepted" string="Uncertain" type="object" class="oe_form_button_active_flow"/>
+                        <button name="do_accept" string="Accept" states="needs-action,tentative,declined" type="object" class="oe_form_button_active_flow"/>
+                        <button name="%(base_calendar.action_view_calendar_invite_attendee_wizard)d" string="Delegate" type="action" states="needs-action,tentative,declined,accepted" context="{'model' : 'calendar.attendee', 'attendee_field' : 'child_ids'}" />
+                        <button name="do_decline" string="Decline" states="needs-action,tentative,accepted" type="object" class="oe_form_button_active_flow"/>
                         <field name="state" widget="statusbar"
                             statusbar_visible="tentative,needs-action,accepted" statusbar_colors='{"proforma":"blue"}'/>
                     </header>
@@ -211,21 +201,9 @@
             <field name="arch" type="xml">
                 <form string="Events" version="7.0">
                 <header>
-                    <button name="do_confirm"
-                        string="Confirm"
-                        states="tentative,cancelled"
-                        type="object"
-                        />
-                    <button name="do_tentative"
-                        states="confirmed,cancelled"
-                        string="Uncertain"
-                        type="object"
-                        />
-                    <button name="do_cancel"
-                        string="Cancel"
-                        states="tentative,confirmed"
-                        type="object"
-                        />
+                    <button name="do_confirm" string="Confirm" states="tentative,cancelled" type="object" class="oe_form_button_active_flow"/>
+                    <button name="do_tentative" states="confirmed,cancelled" string="Uncertain" type="object" class="oe_form_button_active_flow"/>
+                    <button name="do_cancel" string="Cancel" states="tentative,confirmed" type="object" />
                     <field name="state" widget="statusbar"
                         statusbar_visible="tentative,confirmed" statusbar_colors='{"proforma":"blue"}'/>
                 </header>