diff --git a/src/calendar/gui/e-comp-editor-event.c b/src/calendar/gui/e-comp-editor-event.c
index 33ecb9df83..1a8a96fc19 100644
--- a/src/calendar/gui/e-comp-editor-event.c
+++ b/src/calendar/gui/e-comp-editor-event.c
@@ -82,6 +82,9 @@ ece_event_update_times (ECompEditorEvent *event_editor,
 			event_editor->priv->dtstart,
 			event_editor->priv->dtend,
 			change_end_datetime);
+		e_comp_editor_ensure_same_value_type (E_COMP_EDITOR (event_editor),
+			change_end_datetime ? event_editor->priv->dtstart : event_editor->priv->dtend,
+			change_end_datetime ? event_editor->priv->dtend : event_editor->priv->dtstart);
 	}
 
 	flags = e_comp_editor_get_flags (E_COMP_EDITOR (event_editor));
@@ -145,6 +148,13 @@ ece_event_all_day_toggled_cb (ECompEditorEvent *event_editor)
 
 	edit_widget = e_comp_editor_property_part_get_edit_widget (event_editor->priv->dtstart);
 
+	if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (event_editor->priv->all_day_check))) {
+		gint hour, minute;
+
+		if (!e_date_edit_get_time_of_day (E_DATE_EDIT (edit_widget), &hour, &minute))
+			e_date_edit_set_time_of_day (E_DATE_EDIT (edit_widget), 0, 0);
+	}
+
 	ece_event_update_times (event_editor, E_DATE_EDIT (edit_widget), TRUE);
 
 	e_comp_editor_ensure_changed (E_COMP_EDITOR (event_editor));
diff --git a/src/calendar/gui/e-comp-editor-property-part.c b/src/calendar/gui/e-comp-editor-property-part.c
index 393f0f4aa3..14bb9b408d 100644
--- a/src/calendar/gui/e-comp-editor-property-part.c
+++ b/src/calendar/gui/e-comp-editor-property-part.c
@@ -1119,12 +1119,10 @@ e_comp_editor_property_part_datetime_set_value (ECompEditorPropertyPartDatetime
 
 		if (!i_cal_time_is_date (value))
 			e_date_edit_set_time_of_day (date_edit, i_cal_time_get_hour (value), i_cal_time_get_minute (value));
-		else if (e_date_edit_get_show_time (date_edit))
-			e_date_edit_set_time_of_day (date_edit, 0, 0);
-		else if (e_date_edit_get_allow_no_date_set (date_edit))
+		else if (e_date_edit_get_show_time (date_edit) && e_date_edit_get_allow_no_date_set (date_edit))
 			e_date_edit_set_time_of_day (date_edit, -1, -1);
-
-		e_comp_editor_property_part_datetime_set_date_only (part_datetime, i_cal_time_is_date (value));
+		else
+			e_comp_editor_property_part_datetime_set_date_only (part_datetime, TRUE);
 	}
 
 	g_clear_object (&tmp_value);
diff --git a/src/calendar/gui/e-comp-editor-task.c b/src/calendar/gui/e-comp-editor-task.c
index 96c575961d..262529e8c7 100644
--- a/src/calendar/gui/e-comp-editor-task.c
+++ b/src/calendar/gui/e-comp-editor-task.c
@@ -50,6 +50,8 @@ struct _ECompEditorTaskPrivate {
 
 	gpointer in_the_past_alert;
 	gpointer insensitive_info_alert;
+	gboolean dtstart_is_unset;
+	gboolean due_is_unset;
 };
 
 G_DEFINE_TYPE (ECompEditorTask, e_comp_editor_task, E_TYPE_COMP_EDITOR)
@@ -313,10 +315,14 @@ ece_task_dtstart_changed_cb (EDateEdit *date_edit,
 			     ECompEditorTask *task_editor)
 {
 	ECompEditor *comp_editor;
+	gboolean was_unset;
 
 	g_return_if_fail (E_IS_DATE_EDIT (date_edit));
 	g_return_if_fail (E_IS_COMP_EDITOR_TASK (task_editor));
 
+	was_unset = task_editor->priv->dtstart_is_unset;
+	task_editor->priv->dtstart_is_unset = e_date_edit_get_time (date_edit) == (time_t) -1;
+
 	comp_editor = E_COMP_EDITOR (task_editor);
 
 	if (e_comp_editor_get_updating (comp_editor))
@@ -328,6 +334,16 @@ ece_task_dtstart_changed_cb (EDateEdit *date_edit,
 		task_editor->priv->dtstart, task_editor->priv->due_date,
 		TRUE);
 
+	/* When setting DTSTART for the first time, derive the type from the DUE,
+	   otherwise the DUE has changed the type to the DATE only. */
+	if (was_unset) {
+		e_comp_editor_ensure_same_value_type (E_COMP_EDITOR (task_editor),
+			task_editor->priv->due_date, task_editor->priv->dtstart);
+	} else {
+		e_comp_editor_ensure_same_value_type (E_COMP_EDITOR (task_editor),
+			task_editor->priv->dtstart, task_editor->priv->due_date);
+	}
+
 	e_comp_editor_set_updating (comp_editor, FALSE);
 
 	ece_task_check_dates_in_the_past (task_editor);
@@ -338,10 +354,14 @@ ece_task_due_date_changed_cb (EDateEdit *date_edit,
 			      ECompEditorTask *task_editor)
 {
 	ECompEditor *comp_editor;
+	gboolean was_unset;
 
 	g_return_if_fail (E_IS_DATE_EDIT (date_edit));
 	g_return_if_fail (E_IS_COMP_EDITOR_TASK (task_editor));
 
+	was_unset = task_editor->priv->due_is_unset;
+	task_editor->priv->due_is_unset = e_date_edit_get_time (date_edit) == (time_t) -1;
+
 	comp_editor = E_COMP_EDITOR (task_editor);
 
 	if (e_comp_editor_get_updating (comp_editor))
@@ -353,6 +373,16 @@ ece_task_due_date_changed_cb (EDateEdit *date_edit,
 		task_editor->priv->dtstart, task_editor->priv->due_date,
 		FALSE);
 
+	/* When setting DUE for the first time, derive the type from the DTSTART,
+	   otherwise the DTSTART has changed the type to the DATE only. */
+	if (was_unset) {
+		e_comp_editor_ensure_same_value_type (E_COMP_EDITOR (task_editor),
+			task_editor->priv->dtstart, task_editor->priv->due_date);
+	} else {
+		e_comp_editor_ensure_same_value_type (E_COMP_EDITOR (task_editor),
+			task_editor->priv->due_date, task_editor->priv->dtstart);
+	}
+
 	e_comp_editor_set_updating (comp_editor, FALSE);
 
 	ece_task_check_dates_in_the_past (task_editor);
@@ -666,6 +696,44 @@ ece_task_fill_component (ECompEditor *comp_editor,
 	return TRUE;
 }
 
+static void
+ece_task_all_day_notify_active_cb (GObject *object,
+				   GParamSpec *param,
+				   gpointer user_data)
+{
+	ECompEditorTask *task_editor = user_data;
+	gboolean active = FALSE, visible = FALSE;
+
+	g_object_get (object,
+		"active", &active,
+		"visible", &visible,
+		NULL);
+
+	if (!active && visible) {
+		EDateEdit *dtstart_date_edit;
+
+		dtstart_date_edit = E_DATE_EDIT (e_comp_editor_property_part_get_edit_widget (task_editor->priv->dtstart));
+
+		if (e_date_edit_get_time (dtstart_date_edit) != (time_t) -1) {
+			EDateEdit *due_date_edit;
+
+			due_date_edit = E_DATE_EDIT (e_comp_editor_property_part_get_edit_widget (task_editor->priv->due_date));
+
+			if (e_date_edit_get_time (due_date_edit) != (time_t) -1) {
+				gint hour, minute;
+
+				if (e_date_edit_get_time_of_day (dtstart_date_edit, &hour, &minute) !=
+				    e_date_edit_get_time_of_day (due_date_edit, &hour, &minute)) {
+					if (e_date_edit_get_time_of_day (dtstart_date_edit, &hour, &minute))
+						e_date_edit_set_time_of_day (due_date_edit, hour, minute);
+					else
+						e_date_edit_set_time_of_day (due_date_edit, -1, -1);
+				}
+			}
+		}
+	}
+}
+
 static void
 ece_task_setup_ui (ECompEditorTask *task_editor)
 {
@@ -784,6 +852,9 @@ ece_task_setup_ui (ECompEditorTask *task_editor)
 		action, "active",
 		edit_widget, "show-time",
 		G_BINDING_INVERT_BOOLEAN);
+
+	e_signal_connect_notify (action, "notify::active",
+		G_CALLBACK (ece_task_all_day_notify_active_cb), task_editor);
 }
 
 static void
diff --git a/src/calendar/gui/e-comp-editor.c b/src/calendar/gui/e-comp-editor.c
index a4b8dae976..16b3e15204 100644
--- a/src/calendar/gui/e-comp-editor.c
+++ b/src/calendar/gui/e-comp-editor.c
@@ -3543,6 +3543,53 @@ e_comp_editor_ensure_start_before_end (ECompEditor *comp_editor,
 	g_clear_object (&end_tt);
 }
 
+void
+e_comp_editor_ensure_same_value_type (ECompEditor *comp_editor,
+				      ECompEditorPropertyPart *src_datetime,
+				      ECompEditorPropertyPart *des_datetime)
+{
+	ECompEditorPropertyPartDatetime *src_dtm, *des_dtm;
+	ICalTime *src_tt, *des_tt;
+
+	g_return_if_fail (E_IS_COMP_EDITOR (comp_editor));
+	g_return_if_fail (E_IS_COMP_EDITOR_PROPERTY_PART_DATETIME (src_datetime));
+	g_return_if_fail (E_IS_COMP_EDITOR_PROPERTY_PART_DATETIME (des_datetime));
+
+	src_dtm = E_COMP_EDITOR_PROPERTY_PART_DATETIME (src_datetime);
+	des_dtm = E_COMP_EDITOR_PROPERTY_PART_DATETIME (des_datetime);
+
+	src_tt = e_comp_editor_property_part_datetime_get_value (src_dtm);
+	des_tt = e_comp_editor_property_part_datetime_get_value (des_dtm);
+
+	if (!src_tt || !des_tt ||
+	    i_cal_time_is_null_time (src_tt) ||
+	    i_cal_time_is_null_time (des_tt) ||
+	    !i_cal_time_is_valid_time (src_tt) ||
+	    !i_cal_time_is_valid_time (des_tt)) {
+		g_clear_object (&src_tt);
+		g_clear_object (&des_tt);
+		return;
+	}
+
+	if (i_cal_time_is_date (src_tt) != i_cal_time_is_date (des_tt)) {
+		gint hour = 0, minute = 0, second = 0;
+
+		i_cal_time_set_is_date (des_tt, i_cal_time_is_date (src_tt));
+
+		if (!i_cal_time_is_date (des_tt)) {
+			i_cal_time_get_time (src_tt, &hour, &minute, &second);
+			i_cal_time_set_time (des_tt, hour, minute, second);
+		}
+
+		e_comp_editor_set_updating (comp_editor, TRUE);
+		e_comp_editor_property_part_datetime_set_value (des_dtm, des_tt);
+		e_comp_editor_set_updating (comp_editor, FALSE);
+	}
+
+	g_clear_object (&src_tt);
+	g_clear_object (&des_tt);
+}
+
 static gboolean
 e_comp_editor_holds_component (ECompEditor *comp_editor,
 			       ESource *origin_source,
diff --git a/src/calendar/gui/e-comp-editor.h b/src/calendar/gui/e-comp-editor.h
index 8973040bcb..1f262d0591 100644
--- a/src/calendar/gui/e-comp-editor.h
+++ b/src/calendar/gui/e-comp-editor.h
@@ -172,6 +172,10 @@ void		e_comp_editor_ensure_start_before_end
 						 ECompEditorPropertyPart *start_datetime,
 						 ECompEditorPropertyPart *end_datetime,
 						 gboolean change_end_datetime);
+void		e_comp_editor_ensure_same_value_type
+						(ECompEditor *comp_editor,
+						 ECompEditorPropertyPart *src_datetime,
+						 ECompEditorPropertyPart *des_datetime);
 ECompEditor *	e_comp_editor_open_for_component
 						(GtkWindow *parent,
 						 EShell *shell,