diff --git a/calendar/templates/default/app.css b/calendar/templates/default/app.css
index 366104f7ab..7953a8210d 100644
--- a/calendar/templates/default/app.css
+++ b/calendar/templates/default/app.css
@@ -295,9 +295,10 @@ e.g. the div with class calendar_calTimeGrid is generated by the timeGridWidget
 .calendar_calGridHeader > div {
 	position: relative;
 	height: 100%;
-	margin-left: 43px;
+	margin-left: 42px;
 	width: initial;
 	white-space: nowrap;
+	border-left: 1px solid silver;
 }
 .calendar_calGridHeader > label {
 	float: left;